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 $164.58   11.759%   $183.933   $183.93   $183.95   $183.90  
  Purchase #2 $147.66   5.116%   $155.2143   $155.21   $155.20   $155.20  
  Purchase #3 $10.73   9.254%   $11.723   $11.72   $11.70   $11.70  
  Purchase #4 $91.70   5.444%   $96.6921   $96.69   $96.70   $96.70  
  Purchase #5 $161.83   6.400%   $172.1871   $172.19   $172.20   $172.20  
  Purchase #6 $191.83   6.329%   $203.9709   $203.97   $203.95   $204.00  
  Purchase #7 $192.53   9.660%   $211.1284   $211.13   $211.15   $211.10  
  7 purchase totals = $960.86       $1,034.8488   $1,034.84   $1,034.85   $1,034.80