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	$32.29	10.627%	$35.7215	$35.72	$35.70	$35.70
Purchase #2	$28.49	8.194%	$30.8245	$30.82	$30.80	$30.80
Purchase #3	$68.90	5.308%	$72.5572	$72.56	$72.55	$72.60
Purchase #4	$133.78	7.551%	$143.8817	$143.88	$143.90	$143.90
Purchase #5	$111.67	7.190%	$119.6991	$119.70	$119.70	$119.70
Purchase #6	$160.60	12.385%	$180.4903	$180.49	$180.50	$180.50
Purchase #7	$247.39	5.614%	$261.2785	$261.28	$261.30	$261.30
7 purchase totals =	$783.12		$844.4528	$844.45	$844.45	$844.50