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 $161.78   8.133%   $174.9376   $174.94   $174.95   $174.90  
  Purchase #2 $60.44   13.376%   $68.5245   $68.52   $68.50   $68.50  
  Purchase #3 $73.60   11.240%   $81.8726   $81.87   $81.85   $81.90  
  Purchase #4 $127.47   9.704%   $139.8397   $139.84   $139.85   $139.80  
  Purchase #5 $184.91   10.864%   $204.9986   $205.00   $205.00   $205.00  
  Purchase #6 $149.42   9.295%   $163.3086   $163.31   $163.30   $163.30  
  Purchase #7 $211.50   7.373%   $227.0939   $227.09   $227.10   $227.10  
  7 purchase totals = $969.12       $1,060.5755   $1,060.57   $1,060.55   $1,060.50