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	$221.43	4.709%	$231.8571	$231.86	$231.85	$231.90
Purchase #2	$130.44	11.676%	$145.6702	$145.67	$145.65	$145.70
Purchase #3	$158.61	4.413%	$165.6095	$165.61	$165.60	$165.60
Purchase #4	$116.34	10.652%	$128.7325	$128.73	$128.75	$128.70
Purchase #5	$176.65	7.792%	$190.4146	$190.41	$190.40	$190.40
Purchase #6	$92.77	3.248%	$95.7832	$95.78	$95.80	$95.80
Purchase #7	$105.38	12.134%	$118.1668	$118.17	$118.15	$118.20
7 purchase totals =	$1,001.62		$1,076.2339	$1,076.23	$1,076.20	$1,076.30