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	$168.68	12.231%	$189.3113	$189.31	$189.30	$189.30
Purchase #2	$121.64	13.559%	$138.1332	$138.13	$138.15	$138.10
Purchase #3	$125.64	4.611%	$131.4333	$131.43	$131.45	$131.40
Purchase #4	$100.76	7.852%	$108.6717	$108.67	$108.65	$108.70
Purchase #5	$238.66	7.496%	$256.55	$256.55	$256.55	$256.60
Purchase #6	$123.71	5.691%	$130.7503	$130.75	$130.75	$130.80
Purchase #7	$158.29	6.703%	$168.9002	$168.90	$168.90	$168.90
7 purchase totals =	$1,037.38		$1,123.7500	$1,123.74	$1,123.75	$1,123.80