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	$203.66	8.777%	$221.5352	$221.54	$221.55	$221.50
Purchase #2	$81.58	8.189%	$88.2606	$88.26	$88.25	$88.30
Purchase #3	$139.72	10.335%	$154.1601	$154.16	$154.15	$154.20
Purchase #4	$213.69	11.429%	$238.1126	$238.11	$238.10	$238.10
Purchase #5	$150.53	4.654%	$157.5357	$157.54	$157.55	$157.50
Purchase #6	$56.92	7.797%	$61.3581	$61.36	$61.35	$61.40
Purchase #7	$165.94	5.111%	$174.4212	$174.42	$174.40	$174.40
7 purchase totals =	$1,012.04		$1,095.3835	$1,095.39	$1,095.35	$1,095.40