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	$47.55	13.391%	$53.9174	$53.92	$53.90	$53.90
Purchase #2	$65.57	10.595%	$72.5171	$72.52	$72.50	$72.50
Purchase #3	$151.48	11.307%	$168.6078	$168.61	$168.60	$168.60
Purchase #4	$42.77	8.611%	$46.4529	$46.45	$46.45	$46.50
Purchase #5	$79.85	4.568%	$83.4975	$83.50	$83.50	$83.50
Purchase #6	$183.89	11.170%	$204.4305	$204.43	$204.45	$204.40
Purchase #7	$66.34	11.786%	$74.1588	$74.16	$74.15	$74.20
7 purchase totals =	$637.45		$703.5820	$703.59	$703.55	$703.60