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	$201.71	4.484%	$210.7547	$210.75	$210.75	$210.80
Purchase #2	$145.79	4.707%	$152.6523	$152.65	$152.65	$152.70
Purchase #3	$238.93	13.462%	$271.0948	$271.09	$271.10	$271.10
Purchase #4	$92.91	6.613%	$99.0541	$99.05	$99.05	$99.10
Purchase #5	$169.96	6.813%	$181.5394	$181.54	$181.55	$181.50
Purchase #6	$12.26	10.279%	$13.5202	$13.52	$13.50	$13.50
Purchase #7	$33.85	11.697%	$37.8094	$37.81	$37.80	$37.80
7 purchase totals =	$895.41		$966.4249	$966.41	$966.40	$966.50