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	$162.71	8.252%	$176.1368	$176.14	$176.15	$176.10
Purchase #2	$85.72	12.633%	$96.549	$96.55	$96.55	$96.50
Purchase #3	$107.35	9.147%	$117.1693	$117.17	$117.15	$117.20
Purchase #4	$245.27	8.417%	$265.9144	$265.91	$265.90	$265.90
Purchase #5	$241.59	13.526%	$274.2675	$274.27	$274.25	$274.30
Purchase #6	$124.82	11.572%	$139.2642	$139.26	$139.25	$139.30
Purchase #7	$10.27	6.826%	$10.971	$10.97	$10.95	$11.00
7 purchase totals =	$977.73		$1,080.2722	$1,080.27	$1,080.20	$1,080.30