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	$48.64	13.505%	$55.2088	$55.21	$55.20	$55.20
Purchase #2	$184.34	7.449%	$198.0715	$198.07	$198.05	$198.10
Purchase #3	$160.56	5.130%	$168.7967	$168.80	$168.80	$168.80
Purchase #4	$178.56	3.838%	$185.4131	$185.41	$185.40	$185.40
Purchase #5	$133.68	13.532%	$151.7696	$151.77	$151.75	$151.80
Purchase #6	$79.48	5.117%	$83.547	$83.55	$83.55	$83.50
Purchase #7	$176.28	7.123%	$188.8364	$188.84	$188.85	$188.80
7 purchase totals =	$961.54		$1,031.6431	$1,031.65	$1,031.60	$1,031.60