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	$216.67	5.374%	$228.3138	$228.31	$228.30	$228.30
Purchase #2	$134.34	11.353%	$149.5916	$149.59	$149.60	$149.60
Purchase #3	$169.98	5.584%	$179.4717	$179.47	$179.45	$179.50
Purchase #4	$103.94	4.772%	$108.9	$108.90	$108.90	$108.90
Purchase #5	$10.25	6.228%	$10.8884	$10.89	$10.90	$10.90
Purchase #6	$45.80	10.473%	$50.5966	$50.60	$50.60	$50.60
Purchase #7	$197.25	6.812%	$210.6867	$210.69	$210.70	$210.70
7 purchase totals =	$878.23		$938.4488	$938.45	$938.45	$938.50