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	$243.96	4.499%	$254.9358	$254.94	$254.95	$254.90
Purchase #2	$85.56	11.673%	$95.5474	$95.55	$95.55	$95.50
Purchase #3	$195.55	7.869%	$210.9378	$210.94	$210.95	$210.90
Purchase #4	$233.45	5.203%	$245.5964	$245.60	$245.60	$245.60
Purchase #5	$115.71	10.686%	$128.0748	$128.07	$128.05	$128.10
Purchase #6	$33.87	9.513%	$37.0921	$37.09	$37.10	$37.10
Purchase #7	$144.88	9.673%	$158.8942	$158.89	$158.90	$158.90
7 purchase totals =	$1,052.98		$1,131.0785	$1,131.08	$1,131.10	$1,131.00