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	$39.35	12.655%	$44.3297	$44.33	$44.35	$44.30
Purchase #2	$84.30	7.782%	$90.8602	$90.86	$90.85	$90.90
Purchase #3	$118.80	7.859%	$128.1365	$128.14	$128.15	$128.10
Purchase #4	$205.93	8.267%	$222.9542	$222.95	$222.95	$223.00
Purchase #5	$147.89	11.803%	$165.3455	$165.35	$165.35	$165.30
Purchase #6	$14.74	3.742%	$15.2916	$15.29	$15.30	$15.30
Purchase #7	$84.71	3.772%	$87.9053	$87.91	$87.90	$87.90
7 purchase totals =	$695.72		$754.8230	$754.83	$754.85	$754.80