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	$144.90	8.769%	$157.6063	$157.61	$157.60	$157.60
Purchase #2	$124.72	13.639%	$141.7306	$141.73	$141.75	$141.70
Purchase #3	$83.56	9.223%	$91.2667	$91.27	$91.25	$91.30
Purchase #4	$188.29	3.698%	$195.253	$195.25	$195.25	$195.30
Purchase #5	$52.48	3.791%	$54.4695	$54.47	$54.45	$54.50
Purchase #6	$113.27	8.215%	$122.5751	$122.58	$122.60	$122.60
Purchase #7	$129.95	3.531%	$134.5385	$134.54	$134.55	$134.50
7 purchase totals =	$837.17		$897.4397	$897.45	$897.45	$897.50