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	$120.74	13.361%	$136.8721	$136.87	$136.85	$136.90
Purchase #2	$139.63	8.476%	$151.465	$151.47	$151.45	$151.50
Purchase #3	$149.79	6.631%	$159.7226	$159.72	$159.70	$159.70
Purchase #4	$236.70	4.190%	$246.6177	$246.62	$246.60	$246.60
Purchase #5	$76.94	11.370%	$85.6881	$85.69	$85.70	$85.70
Purchase #6	$176.56	11.331%	$196.566	$196.57	$196.55	$196.60
Purchase #7	$173.79	6.462%	$185.0203	$185.02	$185.00	$185.00
7 purchase totals =	$1,074.15		$1,161.9518	$1,161.96	$1,161.85	$1,162.00