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	$212.90	5.750%	$225.1418	$225.14	$225.15	$225.10
Purchase #2	$42.91	7.650%	$46.1926	$46.19	$46.20	$46.20
Purchase #3	$103.77	4.204%	$108.1325	$108.13	$108.15	$108.10
Purchase #4	$142.60	4.788%	$149.4277	$149.43	$149.45	$149.40
Purchase #5	$66.82	8.835%	$72.7235	$72.72	$72.70	$72.70
Purchase #6	$74.97	10.145%	$82.5757	$82.58	$82.60	$82.60
Purchase #7	$238.40	11.475%	$265.7564	$265.76	$265.75	$265.80
7 purchase totals =	$882.37		$949.9502	$949.95	$950.00	$949.90