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	$218.49	3.364%	$225.84	$225.84	$225.85	$225.80
Purchase #2	$95.74	7.148%	$102.5835	$102.58	$102.60	$102.60
Purchase #3	$129.81	6.196%	$137.853	$137.85	$137.85	$137.90
Purchase #4	$72.77	8.133%	$78.6884	$78.69	$78.70	$78.70
Purchase #5	$63.91	10.834%	$70.834	$70.83	$70.85	$70.80
Purchase #6	$213.69	4.599%	$223.5176	$223.52	$223.50	$223.50
Purchase #7	$83.83	9.517%	$91.8081	$91.81	$91.80	$91.80
7 purchase totals =	$878.24		$931.1246	$931.12	$931.15	$931.10