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	$214.56	11.269%	$238.7388	$238.74	$238.75	$238.70
Purchase #2	$88.96	4.153%	$92.6545	$92.65	$92.65	$92.70
Purchase #3	$199.44	12.761%	$224.8905	$224.89	$224.90	$224.90
Purchase #4	$114.33	8.727%	$124.3076	$124.31	$124.30	$124.30
Purchase #5	$235.47	8.370%	$255.1788	$255.18	$255.20	$255.20
Purchase #6	$213.46	4.135%	$222.2866	$222.29	$222.30	$222.30
Purchase #7	$218.33	11.442%	$243.3113	$243.31	$243.30	$243.30
7 purchase totals =	$1,284.55		$1,401.3681	$1,401.37	$1,401.40	$1,401.40