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	$122.76	6.321%	$130.5197	$130.52	$130.50	$130.50
Purchase #2	$191.61	13.629%	$217.7245	$217.72	$217.70	$217.70
Purchase #3	$64.91	4.173%	$67.6187	$67.62	$67.60	$67.60
Purchase #4	$31.38	13.110%	$35.4939	$35.49	$35.50	$35.50
Purchase #5	$235.66	5.418%	$248.4281	$248.43	$248.45	$248.40
Purchase #6	$186.47	12.836%	$210.4053	$210.41	$210.40	$210.40
Purchase #7	$134.82	6.653%	$143.7896	$143.79	$143.80	$143.80
7 purchase totals =	$967.61		$1,053.9798	$1,053.98	$1,053.95	$1,053.90