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	$38.55	11.152%	$42.8491	$42.85	$42.85	$42.80
Purchase #2	$142.84	6.121%	$151.5832	$151.58	$151.60	$151.60
Purchase #3	$9.46	11.353%	$10.534	$10.53	$10.55	$10.50
Purchase #4	$85.55	8.105%	$92.4838	$92.48	$92.50	$92.50
Purchase #5	$23.54	9.596%	$25.7989	$25.80	$25.80	$25.80
Purchase #6	$118.87	4.280%	$123.9576	$123.96	$123.95	$124.00
Purchase #7	$45.59	11.213%	$50.702	$50.70	$50.70	$50.70
7 purchase totals =	$464.40		$497.9086	$497.90	$497.95	$497.90