Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $35.70   3.819%   $37.0634   $37.06   $37.05   $37.10  
  Purchase #2 $179.27   10.272%   $197.6846   $197.68   $197.70   $197.70  
  Purchase #3 $245.39   5.158%   $258.0472   $258.05   $258.05   $258.00  
  Purchase #4 $118.54   7.628%   $127.5822   $127.58   $127.60   $127.60  
  Purchase #5 $171.88   12.560%   $193.4681   $193.47   $193.45   $193.50  
  Purchase #6 $53.46   5.540%   $56.4217   $56.42   $56.40   $56.40  
  Purchase #7 $218.57   11.696%   $244.1339   $244.13   $244.15   $244.10  
  7 purchase totals = $1,022.81       $1,114.4011   $1,114.39   $1,114.40   $1,114.40