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	$234.87	4.682%	$245.8666	$245.87	$245.85	$245.90
Purchase #2	$211.70	8.281%	$229.2309	$229.23	$229.25	$229.20
Purchase #3	$145.51	6.208%	$154.5433	$154.54	$154.55	$154.50
Purchase #4	$144.79	6.565%	$154.2955	$154.30	$154.30	$154.30
Purchase #5	$107.28	11.476%	$119.5915	$119.59	$119.60	$119.60
Purchase #6	$209.67	5.512%	$221.227	$221.23	$221.25	$221.20
Purchase #7	$105.34	5.835%	$111.4866	$111.49	$111.50	$111.50
7 purchase totals =	$1,159.16		$1,236.2414	$1,236.25	$1,236.30	$1,236.20