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	$93.63	7.815%	$100.9472	$100.95	$100.95	$100.90
Purchase #2	$34.27	3.568%	$35.4928	$35.49	$35.50	$35.50
Purchase #3	$111.27	10.794%	$123.2805	$123.28	$123.30	$123.30
Purchase #4	$36.29	4.318%	$37.857	$37.86	$37.85	$37.90
Purchase #5	$87.49	7.593%	$94.1331	$94.13	$94.15	$94.10
Purchase #6	$77.67	11.655%	$86.7224	$86.72	$86.70	$86.70
Purchase #7	$38.53	3.148%	$39.7429	$39.74	$39.75	$39.70
7 purchase totals =	$479.15		$518.1759	$518.17	$518.20	$518.10