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	$101.50	9.831%	$111.4785	$111.48	$111.50	$111.50
Purchase #2	$244.84	12.117%	$274.5073	$274.51	$274.50	$274.50
Purchase #3	$157.56	9.140%	$171.961	$171.96	$171.95	$172.00
Purchase #4	$116.49	12.443%	$130.9849	$130.98	$131.00	$131.00
Purchase #5	$196.62	12.235%	$220.6765	$220.68	$220.70	$220.70
Purchase #6	$149.93	13.287%	$169.8512	$169.85	$169.85	$169.90
Purchase #7	$138.88	11.677%	$155.097	$155.10	$155.10	$155.10
7 purchase totals =	$1,105.82		$1,234.5564	$1,234.56	$1,234.60	$1,234.70