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	$153.43	11.406%	$170.9302	$170.93	$170.95	$170.90
Purchase #2	$196.34	4.353%	$204.8867	$204.89	$204.90	$204.90
Purchase #3	$136.78	11.494%	$152.5015	$152.50	$152.50	$152.50
Purchase #4	$173.55	10.323%	$191.4656	$191.47	$191.45	$191.50
Purchase #5	$250.40	5.561%	$264.3247	$264.32	$264.30	$264.30
Purchase #6	$142.86	5.844%	$151.2087	$151.21	$151.20	$151.20
Purchase #7	$33.99	11.180%	$37.7901	$37.79	$37.80	$37.80
7 purchase totals =	$1,087.35		$1,173.1075	$1,173.11	$1,173.10	$1,173.10