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	$33.29	6.458%	$35.4399	$35.44	$35.45	$35.40
Purchase #2	$136.90	10.646%	$151.4744	$151.47	$151.45	$151.50
Purchase #3	$61.78	7.185%	$66.2189	$66.22	$66.20	$66.20
Purchase #4	$163.65	9.435%	$179.0904	$179.09	$179.10	$179.10
Purchase #5	$35.73	13.787%	$40.6561	$40.66	$40.65	$40.70
Purchase #6	$12.44	6.559%	$13.2559	$13.26	$13.25	$13.30
Purchase #7	$242.63	13.648%	$275.7441	$275.74	$275.75	$275.70
7 purchase totals =	$686.42		$761.8797	$761.88	$761.85	$761.90