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	$172.29	10.125%	$189.7344	$189.73	$189.75	$189.70
Purchase #2	$161.96	11.588%	$180.7279	$180.73	$180.75	$180.70
Purchase #3	$148.75	11.182%	$165.3832	$165.38	$165.40	$165.40
Purchase #4	$88.59	13.405%	$100.4655	$100.47	$100.45	$100.50
Purchase #5	$225.81	9.789%	$247.9145	$247.91	$247.90	$247.90
Purchase #6	$250.83	5.403%	$264.3823	$264.38	$264.40	$264.40
Purchase #7	$238.97	3.682%	$247.7689	$247.77	$247.75	$247.80
7 purchase totals =	$1,287.20		$1,396.3767	$1,396.37	$1,396.40	$1,396.40