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 $84.66   3.560%   $87.6739   $87.67   $87.65   $87.70  
  Purchase #2 $179.36   9.452%   $196.3131   $196.31   $196.30   $196.30  
  Purchase #3 $230.85   4.732%   $241.7738   $241.77   $241.75   $241.80  
  Purchase #4 $87.97   3.525%   $91.0709   $91.07   $91.05   $91.10  
  Purchase #5 $61.89   3.727%   $64.1966   $64.20   $64.20   $64.20  
  Purchase #6 $241.74   3.219%   $249.5216   $249.52   $249.50   $249.50  
  Purchase #7 $227.58   3.315%   $235.1243   $235.12   $235.10   $235.10  
  7 purchase totals = $1,114.05       $1,165.6742   $1,165.66   $1,165.55   $1,165.70