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	$85.72	7.497%	$92.1464	$92.15	$92.15	$92.10
Purchase #2	$250.65	6.276%	$266.3808	$266.38	$266.40	$266.40
Purchase #3	$49.79	7.285%	$53.4172	$53.42	$53.40	$53.40
Purchase #4	$28.28	12.107%	$31.7039	$31.70	$31.70	$31.70
Purchase #5	$228.41	7.190%	$244.8327	$244.83	$244.85	$244.80
Purchase #6	$33.78	5.384%	$35.5987	$35.60	$35.60	$35.60
Purchase #7	$159.43	8.826%	$173.5013	$173.50	$173.50	$173.50
7 purchase totals =	$836.06		$897.5810	$897.58	$897.60	$897.50