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	$183.85	8.264%	$199.0434	$199.04	$199.05	$199.00
Purchase #2	$30.78	7.843%	$33.1941	$33.19	$33.20	$33.20
Purchase #3	$196.75	13.285%	$222.8882	$222.89	$222.90	$222.90
Purchase #4	$231.76	5.634%	$244.8174	$244.82	$244.80	$244.80
Purchase #5	$118.33	11.437%	$131.8634	$131.86	$131.85	$131.90
Purchase #6	$15.36	11.318%	$17.0984	$17.10	$17.10	$17.10
Purchase #7	$119.74	6.680%	$127.7386	$127.74	$127.75	$127.70
7 purchase totals =	$896.57		$976.6435	$976.64	$976.65	$976.60