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	$35.66	5.767%	$37.7165	$37.72	$37.70	$37.70
Purchase #2	$247.83	7.840%	$267.2599	$267.26	$267.25	$267.30
Purchase #3	$93.72	6.580%	$99.8868	$99.89	$99.90	$99.90
Purchase #4	$40.48	8.420%	$43.8884	$43.89	$43.90	$43.90
Purchase #5	$226.85	6.310%	$241.1642	$241.16	$241.15	$241.20
Purchase #6	$190.79	4.629%	$199.6217	$199.62	$199.60	$199.60
Purchase #7	$169.98	13.675%	$193.2248	$193.22	$193.20	$193.20
7 purchase totals =	$1,005.31		$1,082.7623	$1,082.76	$1,082.70	$1,082.80