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	$137.91	8.806%	$150.0544	$150.05	$150.05	$150.10
Purchase #2	$83.64	9.470%	$91.5607	$91.56	$91.55	$91.60
Purchase #3	$37.60	5.189%	$39.5511	$39.55	$39.55	$39.60
Purchase #4	$71.28	10.779%	$78.9633	$78.96	$78.95	$79.00
Purchase #5	$161.64	10.465%	$178.5556	$178.56	$178.55	$178.60
Purchase #6	$229.67	10.517%	$253.8244	$253.82	$253.80	$253.80
Purchase #7	$192.46	11.851%	$215.2684	$215.27	$215.25	$215.30
7 purchase totals =	$914.20		$1,007.7779	$1,007.77	$1,007.70	$1,008.00