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	$66.60	7.596%	$71.6589	$71.66	$71.65	$71.70
Purchase #2	$124.78	13.309%	$141.387	$141.39	$141.40	$141.40
Purchase #3	$164.74	11.306%	$183.3655	$183.37	$183.35	$183.40
Purchase #4	$130.73	4.576%	$136.7122	$136.71	$136.70	$136.70
Purchase #5	$22.32	9.114%	$24.3542	$24.35	$24.35	$24.40
Purchase #6	$79.80	11.809%	$89.2236	$89.22	$89.20	$89.20
Purchase #7	$74.99	4.169%	$78.1163	$78.12	$78.10	$78.10
7 purchase totals =	$663.96		$724.8177	$724.82	$724.75	$724.90