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	$20.71	5.326%	$21.813	$21.81	$21.80	$21.80
Purchase #2	$11.67	3.809%	$12.1145	$12.11	$12.10	$12.10
Purchase #3	$52.90	11.769%	$59.1258	$59.13	$59.15	$59.10
Purchase #4	$55.37	4.559%	$57.8943	$57.89	$57.90	$57.90
Purchase #5	$77.53	7.180%	$83.0967	$83.10	$83.10	$83.10
Purchase #6	$25.86	7.689%	$27.8484	$27.85	$27.85	$27.80
Purchase #7	$99.93	8.734%	$108.6579	$108.66	$108.65	$108.70
7 purchase totals =	$343.97		$370.5506	$370.55	$370.55	$370.50