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	$100.46	11.440%	$111.9526	$111.95	$111.95	$112.00
Purchase #2	$129.92	5.240%	$136.7278	$136.73	$136.75	$136.70
Purchase #3	$62.94	10.866%	$69.7791	$69.78	$69.80	$69.80
Purchase #4	$38.35	9.731%	$42.0818	$42.08	$42.10	$42.10
Purchase #5	$83.57	11.825%	$93.4522	$93.45	$93.45	$93.50
Purchase #6	$50.92	8.837%	$55.4198	$55.42	$55.40	$55.40
Purchase #7	$20.51	9.489%	$22.4562	$22.46	$22.45	$22.50
7 purchase totals =	$486.67		$531.8695	$531.87	$531.90	$532.00