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	$179.26	9.488%	$196.2682	$196.27	$196.25	$196.30
Purchase #2	$18.70	12.570%	$21.0506	$21.05	$21.05	$21.10
Purchase #3	$89.51	11.192%	$99.528	$99.53	$99.55	$99.50
Purchase #4	$218.93	4.171%	$228.0616	$228.06	$228.05	$228.10
Purchase #5	$55.74	4.363%	$58.1719	$58.17	$58.15	$58.20
Purchase #6	$159.55	12.583%	$179.6262	$179.63	$179.65	$179.60
Purchase #7	$99.70	13.259%	$112.9192	$112.92	$112.90	$112.90
7 purchase totals =	$821.39		$895.6257	$895.63	$895.60	$895.70