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	$35.39	5.268%	$37.2543	$37.25	$37.25	$37.30
Purchase #2	$51.34	5.720%	$54.2766	$54.28	$54.30	$54.30
Purchase #3	$176.62	4.579%	$184.7074	$184.71	$184.70	$184.70
Purchase #4	$146.54	3.665%	$151.9107	$151.91	$151.90	$151.90
Purchase #5	$14.66	3.365%	$15.1533	$15.15	$15.15	$15.20
Purchase #6	$36.50	9.851%	$40.0956	$40.10	$40.10	$40.10
Purchase #7	$244.84	5.437%	$258.152	$258.15	$258.15	$258.20
7 purchase totals =	$705.89		$741.5499	$741.55	$741.55	$741.70