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	$240.27	8.801%	$261.4162	$261.42	$261.40	$261.40
Purchase #2	$240.25	6.597%	$256.0993	$256.10	$256.10	$256.10
Purchase #3	$147.70	11.597%	$164.8288	$164.83	$164.85	$164.80
Purchase #4	$81.97	4.773%	$85.8824	$85.88	$85.90	$85.90
Purchase #5	$172.65	5.503%	$182.1509	$182.15	$182.15	$182.20
Purchase #6	$14.39	4.501%	$15.0377	$15.04	$15.05	$15.00
Purchase #7	$60.44	11.613%	$67.4589	$67.46	$67.45	$67.50
7 purchase totals =	$957.67		$1,032.8742	$1,032.88	$1,032.90	$1,032.90