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	$88.65	4.229%	$92.399	$92.40	$92.40	$92.40
Purchase #2	$217.84	12.141%	$244.288	$244.29	$244.30	$244.30
Purchase #3	$185.98	7.263%	$199.4877	$199.49	$199.50	$199.50
Purchase #4	$53.57	12.698%	$60.3723	$60.37	$60.35	$60.40
Purchase #5	$79.78	13.499%	$90.5495	$90.55	$90.55	$90.50
Purchase #6	$135.45	4.862%	$142.0356	$142.04	$142.05	$142.00
Purchase #7	$112.91	11.705%	$126.1261	$126.13	$126.15	$126.10
7 purchase totals =	$874.18		$955.2582	$955.27	$955.30	$955.20