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	$137.57	11.862%	$153.8886	$153.89	$153.90	$153.90
Purchase #2	$57.83	8.589%	$62.797	$62.80	$62.80	$62.80
Purchase #3	$195.87	6.476%	$208.5545	$208.55	$208.55	$208.60
Purchase #4	$104.68	4.680%	$109.579	$109.58	$109.60	$109.60
Purchase #5	$28.52	3.119%	$29.4095	$29.41	$29.40	$29.40
Purchase #6	$7.51	5.250%	$7.9043	$7.90	$7.90	$7.90
Purchase #7	$183.53	4.441%	$191.6806	$191.68	$191.70	$191.70
7 purchase totals =	$715.51		$763.8135	$763.81	$763.85	$763.90