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	$114.83	7.133%	$123.0208	$123.02	$123.00	$123.00
Purchase #2	$231.33	10.232%	$254.9997	$255.00	$255.00	$255.00
Purchase #3	$59.39	5.167%	$62.4587	$62.46	$62.45	$62.50
Purchase #4	$237.62	3.647%	$246.286	$246.29	$246.30	$246.30
Purchase #5	$26.36	10.207%	$29.0506	$29.05	$29.05	$29.10
Purchase #6	$151.89	4.750%	$159.1048	$159.10	$159.10	$159.10
Purchase #7	$85.55	5.483%	$90.2407	$90.24	$90.25	$90.20
7 purchase totals =	$906.97		$965.1613	$965.16	$965.15	$965.20