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	$178.67	11.670%	$199.5208	$199.52	$199.50	$199.50
Purchase #2	$10.50	9.729%	$11.5215	$11.52	$11.50	$11.50
Purchase #3	$171.92	9.756%	$188.6925	$188.69	$188.70	$188.70
Purchase #4	$93.28	12.138%	$104.6023	$104.60	$104.60	$104.60
Purchase #5	$145.69	5.595%	$153.8414	$153.84	$153.85	$153.80
Purchase #6	$151.52	11.398%	$168.7902	$168.79	$168.80	$168.80
Purchase #7	$192.90	4.155%	$200.915	$200.92	$200.90	$200.90
7 purchase totals =	$944.48		$1,027.8837	$1,027.88	$1,027.85	$1,027.80