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	$121.91	4.549%	$127.4557	$127.46	$127.45	$127.50
Purchase #2	$43.78	4.413%	$45.712	$45.71	$45.70	$45.70
Purchase #3	$231.53	4.855%	$242.7708	$242.77	$242.75	$242.80
Purchase #4	$205.77	11.471%	$229.3739	$229.37	$229.35	$229.40
Purchase #5	$18.33	11.869%	$20.5056	$20.51	$20.50	$20.50
Purchase #6	$122.57	3.569%	$126.9445	$126.94	$126.95	$126.90
Purchase #7	$89.61	11.395%	$99.8211	$99.82	$99.80	$99.80
7 purchase totals =	$833.50		$892.5836	$892.58	$892.50	$892.60