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	$98.90	12.572%	$111.3337	$111.33	$111.35	$111.30
Purchase #2	$245.94	3.146%	$253.6773	$253.68	$253.70	$253.70
Purchase #3	$63.61	7.254%	$68.2243	$68.22	$68.20	$68.20
Purchase #4	$94.77	7.146%	$101.5423	$101.54	$101.55	$101.50
Purchase #5	$21.50	4.262%	$22.4163	$22.42	$22.40	$22.40
Purchase #6	$174.90	13.802%	$199.0397	$199.04	$199.05	$199.00
Purchase #7	$228.47	11.790%	$255.4066	$255.41	$255.40	$255.40
7 purchase totals =	$928.09		$1,011.6402	$1,011.64	$1,011.65	$1,011.50