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	$201.43	10.496%	$222.5721	$222.57	$222.55	$222.60
Purchase #2	$6.85	11.240%	$7.6199	$7.62	$7.60	$7.60
Purchase #3	$45.58	8.411%	$49.4137	$49.41	$49.40	$49.40
Purchase #4	$20.89	8.401%	$22.645	$22.65	$22.65	$22.60
Purchase #5	$179.66	8.417%	$194.782	$194.78	$194.80	$194.80
Purchase #6	$209.92	6.143%	$222.8154	$222.82	$222.80	$222.80
Purchase #7	$156.39	7.854%	$168.6729	$168.67	$168.65	$168.70
7 purchase totals =	$820.72		$888.5210	$888.52	$888.45	$888.50