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	$177.88	12.518%	$200.147	$200.15	$200.15	$200.10
Purchase #2	$34.42	8.401%	$37.3116	$37.31	$37.30	$37.30
Purchase #3	$234.38	12.699%	$264.1439	$264.14	$264.15	$264.10
Purchase #4	$242.67	8.614%	$263.5736	$263.57	$263.55	$263.60
Purchase #5	$124.39	4.811%	$130.3744	$130.37	$130.35	$130.40
Purchase #6	$41.32	10.668%	$45.728	$45.73	$45.75	$45.70
Purchase #7	$53.28	11.324%	$59.3134	$59.31	$59.30	$59.30
7 purchase totals =	$908.34		$1,000.5919	$1,000.58	$1,000.55	$1,000.50