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	$40.96	5.772%	$43.3242	$43.32	$43.30	$43.30
Purchase #2	$238.36	8.557%	$258.7565	$258.76	$258.75	$258.80
Purchase #3	$87.32	7.720%	$94.0611	$94.06	$94.05	$94.10
Purchase #4	$61.98	8.605%	$67.3134	$67.31	$67.30	$67.30
Purchase #5	$246.95	11.377%	$275.0455	$275.05	$275.05	$275.00
Purchase #6	$77.74	7.148%	$83.2969	$83.30	$83.30	$83.30
Purchase #7	$135.77	11.664%	$151.6062	$151.61	$151.60	$151.60
7 purchase totals =	$889.08		$973.4038	$973.41	$973.35	$973.40