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	$57.60	7.517%	$61.9298	$61.93	$61.95	$61.90
Purchase #2	$34.99	5.117%	$36.7804	$36.78	$36.80	$36.80
Purchase #3	$132.62	9.271%	$144.9152	$144.92	$144.90	$144.90
Purchase #4	$36.42	7.711%	$39.2283	$39.23	$39.25	$39.20
Purchase #5	$132.89	10.347%	$146.6401	$146.64	$146.65	$146.60
Purchase #6	$241.91	11.562%	$269.8796	$269.88	$269.90	$269.90
Purchase #7	$101.66	9.335%	$111.15	$111.15	$111.15	$111.20
7 purchase totals =	$738.09		$810.5234	$810.53	$810.60	$810.50