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	$63.55	8.806%	$69.1462	$69.15	$69.15	$69.10
Purchase #2	$205.46	6.291%	$218.3855	$218.39	$218.40	$218.40
Purchase #3	$53.56	13.818%	$60.9609	$60.96	$60.95	$61.00
Purchase #4	$93.47	6.160%	$99.2278	$99.23	$99.25	$99.20
Purchase #5	$165.43	4.251%	$172.4624	$172.46	$172.45	$172.50
Purchase #6	$127.83	5.430%	$134.7712	$134.77	$134.75	$134.80
Purchase #7	$37.69	7.266%	$40.4286	$40.43	$40.45	$40.40
7 purchase totals =	$746.99		$795.3826	$795.39	$795.40	$795.40