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	$96.27	5.842%	$101.8941	$101.89	$101.90	$101.90
Purchase #2	$217.42	8.119%	$235.0723	$235.07	$235.05	$235.10
Purchase #3	$35.51	4.323%	$37.0451	$37.05	$37.05	$37.00
Purchase #4	$35.71	7.681%	$38.4529	$38.45	$38.45	$38.50
Purchase #5	$181.34	6.495%	$193.118	$193.12	$193.10	$193.10
Purchase #6	$42.89	11.245%	$47.713	$47.71	$47.70	$47.70
Purchase #7	$28.74	13.496%	$32.6188	$32.62	$32.60	$32.60
7 purchase totals =	$637.88		$685.9142	$685.91	$685.85	$685.90