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	$72.42	13.431%	$82.1467	$82.15	$82.15	$82.10
Purchase #2	$230.64	13.839%	$262.5583	$262.56	$262.55	$262.60
Purchase #3	$120.89	9.353%	$132.1968	$132.20	$132.20	$132.20
Purchase #4	$162.52	5.544%	$171.5301	$171.53	$171.55	$171.50
Purchase #5	$88.57	13.181%	$100.2444	$100.24	$100.25	$100.20
Purchase #6	$195.28	11.637%	$218.0047	$218.00	$218.00	$218.00
Purchase #7	$22.40	13.738%	$25.4773	$25.48	$25.50	$25.50
7 purchase totals =	$892.72		$992.1583	$992.16	$992.20	$992.10