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	$215.97	6.300%	$229.5761	$229.58	$229.60	$229.60
Purchase #2	$78.69	3.190%	$81.2002	$81.20	$81.20	$81.20
Purchase #3	$119.66	7.612%	$128.7685	$128.77	$128.75	$128.80
Purchase #4	$174.87	6.185%	$185.6857	$185.69	$185.70	$185.70
Purchase #5	$75.60	9.389%	$82.6981	$82.70	$82.70	$82.70
Purchase #6	$39.97	3.855%	$41.5108	$41.51	$41.50	$41.50
Purchase #7	$55.57	11.344%	$61.8739	$61.87	$61.85	$61.90
7 purchase totals =	$760.33		$811.3133	$811.32	$811.30	$811.40