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	$161.62	4.769%	$169.3277	$169.33	$169.35	$169.30
Purchase #2	$48.68	10.301%	$53.6945	$53.69	$53.70	$53.70
Purchase #3	$28.87	11.443%	$32.1736	$32.17	$32.15	$32.20
Purchase #4	$187.61	12.858%	$211.7329	$211.73	$211.75	$211.70
Purchase #5	$212.27	4.796%	$222.4505	$222.45	$222.45	$222.50
Purchase #6	$136.57	11.639%	$152.4654	$152.47	$152.45	$152.50
Purchase #7	$9.85	3.181%	$10.1633	$10.16	$10.15	$10.20
7 purchase totals =	$785.47		$852.0079	$852.00	$852.00	$852.10