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	$61.25	10.511%	$67.688	$67.69	$67.70	$67.70
Purchase #2	$161.32	6.543%	$171.8752	$171.88	$171.90	$171.90
Purchase #3	$232.88	11.315%	$259.2304	$259.23	$259.25	$259.20
Purchase #4	$135.60	4.555%	$141.7766	$141.78	$141.80	$141.80
Purchase #5	$130.63	11.823%	$146.0744	$146.07	$146.05	$146.10
Purchase #6	$127.45	7.409%	$136.8928	$136.89	$136.90	$136.90
Purchase #7	$32.30	4.449%	$33.737	$33.74	$33.75	$33.70
7 purchase totals =	$881.43		$957.2744	$957.28	$957.35	$957.30