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	$93.82	12.697%	$105.7323	$105.73	$105.75	$105.70
Purchase #2	$40.90	12.268%	$45.9176	$45.92	$45.90	$45.90
Purchase #3	$98.82	4.660%	$103.425	$103.43	$103.45	$103.40
Purchase #4	$71.85	6.742%	$76.6941	$76.69	$76.70	$76.70
Purchase #5	$194.44	5.444%	$205.0253	$205.03	$205.05	$205.00
Purchase #6	$88.67	6.316%	$94.2704	$94.27	$94.25	$94.30
Purchase #7	$163.51	7.738%	$176.1624	$176.16	$176.15	$176.20
7 purchase totals =	$752.01		$807.2271	$807.23	$807.25	$807.20