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	$247.72	6.627%	$264.1364	$264.14	$264.15	$264.10
Purchase #2	$102.36	9.235%	$111.8129	$111.81	$111.80	$111.80
Purchase #3	$236.40	4.620%	$247.3217	$247.32	$247.30	$247.30
Purchase #4	$245.58	3.133%	$253.274	$253.27	$253.25	$253.30
Purchase #5	$203.85	10.791%	$225.8475	$225.85	$225.85	$225.80
Purchase #6	$40.41	4.789%	$42.3452	$42.35	$42.35	$42.30
Purchase #7	$248.64	3.620%	$257.6408	$257.64	$257.65	$257.60
7 purchase totals =	$1,324.96		$1,402.3785	$1,402.38	$1,402.35	$1,402.20