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	$202.55	4.123%	$210.9011	$210.90	$210.90	$210.90
Purchase #2	$35.88	5.704%	$37.9266	$37.93	$37.95	$37.90
Purchase #3	$123.89	12.725%	$139.655	$139.66	$139.65	$139.70
Purchase #4	$140.43	13.514%	$159.4077	$159.41	$159.40	$159.40
Purchase #5	$157.86	5.465%	$166.487	$166.49	$166.50	$166.50
Purchase #6	$49.96	7.419%	$53.6665	$53.67	$53.65	$53.70
Purchase #7	$37.43	11.277%	$41.651	$41.65	$41.65	$41.70
7 purchase totals =	$748.00		$809.6949	$809.71	$809.70	$809.80