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	$244.51	4.394%	$255.2538	$255.25	$255.25	$255.30
Purchase #2	$236.33	4.472%	$246.8987	$246.90	$246.90	$246.90
Purchase #3	$35.66	12.437%	$40.095	$40.10	$40.10	$40.10
Purchase #4	$24.98	9.529%	$27.3603	$27.36	$27.35	$27.40
Purchase #5	$78.78	12.160%	$88.3596	$88.36	$88.35	$88.40
Purchase #6	$86.30	11.851%	$96.5274	$96.53	$96.55	$96.50
Purchase #7	$222.29	12.155%	$249.3093	$249.31	$249.30	$249.30
7 purchase totals =	$928.85		$1,003.8041	$1,003.81	$1,003.80	$1,003.90