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	$82.93	7.258%	$88.9491	$88.95	$88.95	$88.90
Purchase #2	$232.45	13.582%	$264.0214	$264.02	$264.00	$264.00
Purchase #3	$176.67	3.105%	$182.1556	$182.16	$182.15	$182.20
Purchase #4	$41.83	4.625%	$43.7646	$43.76	$43.75	$43.80
Purchase #5	$163.54	12.583%	$184.1182	$184.12	$184.10	$184.10
Purchase #6	$175.45	5.111%	$184.4172	$184.42	$184.40	$184.40
Purchase #7	$137.89	10.396%	$152.225	$152.23	$152.25	$152.20
7 purchase totals =	$1,010.76		$1,099.6511	$1,099.66	$1,099.60	$1,099.60