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	$10.49	13.740%	$11.9313	$11.93	$11.95	$11.90
Purchase #2	$62.63	13.523%	$71.0995	$71.10	$71.10	$71.10
Purchase #3	$6.95	5.246%	$7.3146	$7.31	$7.30	$7.30
Purchase #4	$74.55	11.140%	$82.8549	$82.85	$82.85	$82.90
Purchase #5	$71.25	9.506%	$78.023	$78.02	$78.00	$78.00
Purchase #6	$124.91	4.203%	$130.16	$130.16	$130.15	$130.20
Purchase #7	$62.56	5.536%	$66.0233	$66.02	$66.00	$66.00
7 purchase totals =	$413.34		$447.4066	$447.39	$447.35	$447.40