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	$77.40	7.323%	$83.068	$83.07	$83.05	$83.10
Purchase #2	$86.80	8.429%	$94.1164	$94.12	$94.10	$94.10
Purchase #3	$62.61	4.455%	$65.3993	$65.40	$65.40	$65.40
Purchase #4	$154.77	5.168%	$162.7685	$162.77	$162.75	$162.80
Purchase #5	$247.84	5.463%	$261.3795	$261.38	$261.40	$261.40
Purchase #6	$233.58	11.102%	$259.5121	$259.51	$259.50	$259.50
Purchase #7	$143.58	7.340%	$154.1188	$154.12	$154.10	$154.10
7 purchase totals =	$1,006.58		$1,080.3626	$1,080.37	$1,080.30	$1,080.40