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	$51.40	4.470%	$53.6976	$53.70	$53.70	$53.70
Purchase #2	$241.60	6.754%	$257.9177	$257.92	$257.90	$257.90
Purchase #3	$243.86	13.764%	$277.4249	$277.42	$277.40	$277.40
Purchase #4	$18.80	9.386%	$20.5646	$20.56	$20.55	$20.60
Purchase #5	$66.60	6.811%	$71.1361	$71.14	$71.15	$71.10
Purchase #6	$225.60	8.183%	$244.0608	$244.06	$244.05	$244.10
Purchase #7	$83.47	9.577%	$91.4639	$91.46	$91.45	$91.50
7 purchase totals =	$931.33		$1,016.2656	$1,016.26	$1,016.20	$1,016.30