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	$111.96	13.835%	$127.4497	$127.45	$127.45	$127.40
Purchase #2	$90.34	3.467%	$93.4721	$93.47	$93.45	$93.50
Purchase #3	$201.80	10.756%	$223.5056	$223.51	$223.50	$223.50
Purchase #4	$114.62	5.355%	$120.7579	$120.76	$120.75	$120.80
Purchase #5	$206.86	4.821%	$216.8327	$216.83	$216.85	$216.80
Purchase #6	$66.72	5.615%	$70.4663	$70.47	$70.45	$70.50
Purchase #7	$38.55	10.211%	$42.4863	$42.49	$42.50	$42.50
7 purchase totals =	$830.85		$894.9706	$894.98	$894.95	$895.00