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	$130.47	13.556%	$148.1565	$148.16	$148.15	$148.20
Purchase #2	$16.83	8.593%	$18.2762	$18.28	$18.30	$18.30
Purchase #3	$243.57	11.421%	$271.3881	$271.39	$271.40	$271.40
Purchase #4	$53.68	10.138%	$59.1221	$59.12	$59.10	$59.10
Purchase #5	$92.56	4.779%	$96.9834	$96.98	$97.00	$97.00
Purchase #6	$40.31	11.764%	$45.0521	$45.05	$45.05	$45.10
Purchase #7	$207.87	11.447%	$231.6649	$231.66	$231.65	$231.70
7 purchase totals =	$785.29		$870.6433	$870.64	$870.65	$870.80