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	$182.62	3.325%	$188.6921	$188.69	$188.70	$188.70
Purchase #2	$188.69	5.738%	$199.517	$199.52	$199.50	$199.50
Purchase #3	$135.78	12.272%	$152.4429	$152.44	$152.45	$152.40
Purchase #4	$34.88	4.252%	$36.3631	$36.36	$36.35	$36.40
Purchase #5	$172.90	10.581%	$191.1945	$191.19	$191.20	$191.20
Purchase #6	$218.90	10.835%	$242.6178	$242.62	$242.60	$242.60
Purchase #7	$79.66	13.485%	$90.4022	$90.40	$90.40	$90.40
7 purchase totals =	$1,013.43		$1,101.2296	$1,101.22	$1,101.20	$1,101.20