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	$111.36	9.666%	$122.1241	$122.12	$122.10	$122.10
Purchase #2	$151.53	13.479%	$171.9547	$171.95	$171.95	$172.00
Purchase #3	$153.91	3.247%	$158.9075	$158.91	$158.90	$158.90
Purchase #4	$101.77	7.774%	$109.6816	$109.68	$109.70	$109.70
Purchase #5	$246.35	10.324%	$271.7832	$271.78	$271.80	$271.80
Purchase #6	$35.87	5.376%	$37.7984	$37.80	$37.80	$37.80
Purchase #7	$83.59	6.342%	$88.8913	$88.89	$88.90	$88.90
7 purchase totals =	$884.38		$961.1408	$961.13	$961.15	$961.20