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	$222.34	9.423%	$243.2911	$243.29	$243.30	$243.30
Purchase #2	$77.86	5.561%	$82.1898	$82.19	$82.20	$82.20
Purchase #3	$100.28	11.434%	$111.746	$111.75	$111.75	$111.70
Purchase #4	$23.71	10.796%	$26.2697	$26.27	$26.25	$26.30
Purchase #5	$159.41	10.809%	$176.6406	$176.64	$176.65	$176.60
Purchase #6	$42.77	5.542%	$45.1403	$45.14	$45.15	$45.10
Purchase #7	$156.71	5.789%	$165.7819	$165.78	$165.80	$165.80
7 purchase totals =	$783.08		$851.0594	$851.06	$851.10	$851.00