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	$82.65	9.231%	$90.2794	$90.28	$90.30	$90.30
Purchase #2	$95.26	5.306%	$100.3145	$100.31	$100.30	$100.30
Purchase #3	$83.67	8.609%	$90.8732	$90.87	$90.85	$90.90
Purchase #4	$247.33	11.836%	$276.604	$276.60	$276.60	$276.60
Purchase #5	$184.28	4.135%	$191.9	$191.90	$191.90	$191.90
Purchase #6	$132.60	7.560%	$142.6246	$142.62	$142.60	$142.60
Purchase #7	$223.69	3.686%	$231.9352	$231.94	$231.95	$231.90
7 purchase totals =	$1,049.48		$1,124.5309	$1,124.52	$1,124.50	$1,124.50