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	$219.68	7.657%	$236.5009	$236.50	$236.50	$236.50
Purchase #2	$229.78	4.634%	$240.428	$240.43	$240.45	$240.40
Purchase #3	$41.77	6.508%	$44.4884	$44.49	$44.50	$44.50
Purchase #4	$139.28	5.230%	$146.5643	$146.56	$146.55	$146.60
Purchase #5	$120.25	8.207%	$130.1189	$130.12	$130.10	$130.10
Purchase #6	$30.50	4.553%	$31.8887	$31.89	$31.90	$31.90
Purchase #7	$93.75	5.178%	$98.6044	$98.60	$98.60	$98.60
7 purchase totals =	$875.01		$928.5936	$928.59	$928.60	$928.60