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	$128.50	3.114%	$132.5015	$132.50	$132.50	$132.50
Purchase #2	$79.39	5.588%	$83.8263	$83.83	$83.85	$83.80
Purchase #3	$147.72	3.451%	$152.8178	$152.82	$152.80	$152.80
Purchase #4	$227.31	13.231%	$257.3854	$257.39	$257.40	$257.40
Purchase #5	$58.72	6.763%	$62.6912	$62.69	$62.70	$62.70
Purchase #6	$49.39	8.803%	$53.7378	$53.74	$53.75	$53.70
Purchase #7	$69.27	10.292%	$76.3993	$76.40	$76.40	$76.40
7 purchase totals =	$760.30		$819.3593	$819.37	$819.40	$819.30