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	$127.41	11.539%	$142.1118	$142.11	$142.10	$142.10
Purchase #2	$56.52	8.583%	$61.3711	$61.37	$61.35	$61.40
Purchase #3	$179.46	11.832%	$200.6937	$200.69	$200.70	$200.70
Purchase #4	$42.62	13.748%	$48.4794	$48.48	$48.50	$48.50
Purchase #5	$200.29	7.198%	$214.7069	$214.71	$214.70	$214.70
Purchase #6	$227.38	7.703%	$244.8951	$244.90	$244.90	$244.90
Purchase #7	$219.89	12.568%	$247.5258	$247.53	$247.55	$247.50
7 purchase totals =	$1,053.57		$1,159.7838	$1,159.79	$1,159.80	$1,159.80