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	$220.48	5.815%	$233.3009	$233.30	$233.30	$233.30
Purchase #2	$72.76	6.651%	$77.5993	$77.60	$77.60	$77.60
Purchase #3	$34.84	7.190%	$37.345	$37.35	$37.35	$37.30
Purchase #4	$135.47	6.434%	$144.1861	$144.19	$144.20	$144.20
Purchase #5	$166.78	5.265%	$175.561	$175.56	$175.55	$175.60
Purchase #6	$64.27	10.690%	$71.1405	$71.14	$71.15	$71.10
Purchase #7	$58.96	12.203%	$66.1549	$66.15	$66.15	$66.20
7 purchase totals =	$753.56		$805.2877	$805.29	$805.30	$805.30