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 $56.34   9.253%   $61.5531   $61.55   $61.55   $61.60  
  Purchase #2 $219.62   12.408%   $246.8704   $246.87   $246.85   $246.90  
  Purchase #3 $207.26   10.130%   $228.2554   $228.26   $228.25   $228.30  
  Purchase #4 $184.87   10.612%   $204.4884   $204.49   $204.50   $204.50  
  Purchase #5 $150.49   3.743%   $156.1228   $156.12   $156.10   $156.10  
  Purchase #6 $49.75   4.746%   $52.1111   $52.11   $52.10   $52.10  
  Purchase #7 $198.61   3.647%   $205.8533   $205.85   $205.85   $205.90  
  7 purchase totals = $1,066.94       $1,155.2545   $1,155.25   $1,155.20   $1,155.40