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	$220.30	8.241%	$238.4549	$238.45	$238.45	$238.50
Purchase #2	$64.87	8.626%	$70.4657	$70.47	$70.45	$70.50
Purchase #3	$9.60	11.654%	$10.7188	$10.72	$10.70	$10.70
Purchase #4	$230.47	8.654%	$250.4149	$250.41	$250.40	$250.40
Purchase #5	$73.90	6.220%	$78.4966	$78.50	$78.50	$78.50
Purchase #6	$113.46	11.756%	$126.7984	$126.80	$126.80	$126.80
Purchase #7	$89.50	3.830%	$92.9279	$92.93	$92.95	$92.90
7 purchase totals =	$802.10		$868.2772	$868.28	$868.25	$868.30