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	$240.34	9.145%	$262.3191	$262.32	$262.30	$262.30
Purchase #2	$151.32	9.637%	$165.9027	$165.90	$165.90	$165.90
Purchase #3	$204.38	10.492%	$225.8235	$225.82	$225.80	$225.80
Purchase #4	$217.90	10.546%	$240.8797	$240.88	$240.90	$240.90
Purchase #5	$146.64	10.726%	$162.3686	$162.37	$162.35	$162.40
Purchase #6	$241.70	9.449%	$264.5382	$264.54	$264.55	$264.50
Purchase #7	$231.56	3.699%	$240.1254	$240.13	$240.15	$240.10
7 purchase totals =	$1,433.84		$1,561.9572	$1,561.96	$1,561.95	$1,561.90