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	$151.29	9.149%	$165.1315	$165.13	$165.15	$165.10
Purchase #2	$78.27	5.381%	$82.4817	$82.48	$82.50	$82.50
Purchase #3	$75.74	13.438%	$85.9179	$85.92	$85.90	$85.90
Purchase #4	$7.52	8.581%	$8.1653	$8.17	$8.15	$8.20
Purchase #5	$202.87	5.449%	$213.9244	$213.92	$213.90	$213.90
Purchase #6	$35.79	10.577%	$39.5755	$39.58	$39.60	$39.60
Purchase #7	$191.79	3.293%	$198.1056	$198.11	$198.10	$198.10
7 purchase totals =	$743.27		$793.3019	$793.31	$793.30	$793.30