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 $92.49   9.558%   $101.3302   $101.33   $101.35   $101.30  
  Purchase #2 $44.37   3.539%   $45.9403   $45.94   $45.95   $45.90  
  Purchase #3 $249.56   13.757%   $283.892   $283.89   $283.90   $283.90  
  Purchase #4 $222.85   6.297%   $236.8829   $236.88   $236.90   $236.90  
  Purchase #5 $35.89   3.135%   $37.0152   $37.02   $37.00   $37.00  
  Purchase #6 $240.42   10.672%   $266.0776   $266.08   $266.10   $266.10  
  Purchase #7 $190.50   6.865%   $203.5778   $203.58   $203.60   $203.60  
  7 purchase totals = $1,076.08       $1,174.7160   $1,174.72   $1,174.80   $1,174.70