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	$104.58	13.535%	$118.7349	$118.73	$118.75	$118.70
Purchase #2	$87.90	13.151%	$99.4597	$99.46	$99.45	$99.50
Purchase #3	$69.65	9.360%	$76.1692	$76.17	$76.15	$76.20
Purchase #4	$242.26	5.738%	$256.1609	$256.16	$256.15	$256.20
Purchase #5	$61.52	11.633%	$68.6766	$68.68	$68.70	$68.70
Purchase #6	$41.72	13.869%	$47.5061	$47.51	$47.50	$47.50
Purchase #7	$179.44	9.482%	$196.4545	$196.45	$196.45	$196.50
7 purchase totals =	$787.07		$863.1619	$863.16	$863.15	$863.30