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	$30.65	4.847%	$32.1356	$32.14	$32.15	$32.10
Purchase #2	$142.78	6.677%	$152.3134	$152.31	$152.30	$152.30
Purchase #3	$240.62	5.321%	$253.4234	$253.42	$253.40	$253.40
Purchase #4	$17.55	5.170%	$18.4573	$18.46	$18.45	$18.50
Purchase #5	$42.80	4.554%	$44.7491	$44.75	$44.75	$44.70
Purchase #6	$129.90	5.227%	$136.6899	$136.69	$136.70	$136.70
Purchase #7	$136.82	7.305%	$146.8147	$146.81	$146.80	$146.80
7 purchase totals =	$741.12		$784.5834	$784.58	$784.55	$784.50