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	$224.81	11.305%	$250.2248	$250.22	$250.20	$250.20
Purchase #2	$224.56	6.309%	$238.7275	$238.73	$238.75	$238.70
Purchase #3	$231.68	10.399%	$255.7724	$255.77	$255.75	$255.80
Purchase #4	$180.76	5.294%	$190.3294	$190.33	$190.35	$190.30
Purchase #5	$18.81	3.570%	$19.4815	$19.48	$19.50	$19.50
Purchase #6	$55.81	13.496%	$63.3421	$63.34	$63.35	$63.30
Purchase #7	$116.84	6.466%	$124.3949	$124.39	$124.40	$124.40
7 purchase totals =	$1,053.27		$1,142.2726	$1,142.26	$1,142.30	$1,142.20