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	$132.79	11.523%	$148.0914	$148.09	$148.10	$148.10
Purchase #2	$78.51	6.808%	$83.855	$83.86	$83.85	$83.90
Purchase #3	$38.27	6.753%	$40.8544	$40.85	$40.85	$40.90
Purchase #4	$188.88	5.441%	$199.157	$199.16	$199.15	$199.20
Purchase #5	$155.77	8.275%	$168.66	$168.66	$168.65	$168.70
Purchase #6	$235.72	8.127%	$254.877	$254.88	$254.90	$254.90
Purchase #7	$81.91	7.358%	$87.9369	$87.94	$87.95	$87.90
7 purchase totals =	$911.85		$983.4317	$983.44	$983.45	$983.60