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	$134.33	12.661%	$151.3375	$151.34	$151.35	$151.30
Purchase #2	$232.58	4.118%	$242.1576	$242.16	$242.15	$242.20
Purchase #3	$95.84	9.446%	$104.893	$104.89	$104.90	$104.90
Purchase #4	$78.28	5.520%	$82.6011	$82.60	$82.60	$82.60
Purchase #5	$98.52	6.485%	$104.909	$104.91	$104.90	$104.90
Purchase #6	$30.38	13.439%	$34.4628	$34.46	$34.45	$34.50
Purchase #7	$22.94	10.519%	$25.3531	$25.35	$25.35	$25.40
7 purchase totals =	$692.87		$745.7141	$745.71	$745.70	$745.80