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 $244.50   7.539%   $262.9329   $262.93   $262.95   $262.90  
  Purchase #2 $143.81   3.427%   $148.7384   $148.74   $148.75   $148.70  
  Purchase #3 $120.82   5.383%   $127.3237   $127.32   $127.30   $127.30  
  Purchase #4 $117.35   3.625%   $121.6039   $121.60   $121.60   $121.60  
  Purchase #5 $7.75   6.630%   $8.2638   $8.26   $8.25   $8.30  
  Purchase #6 $218.52   10.720%   $241.9453   $241.95   $241.95   $241.90  
  Purchase #7 $142.35   5.232%   $149.7978   $149.80   $149.80   $149.80  
  7 purchase totals = $995.10       $1,060.6058   $1,060.60   $1,060.60   $1,060.50