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	$187.69	13.386%	$212.8142	$212.81	$212.80	$212.80
Purchase #2	$76.56	7.723%	$82.4727	$82.47	$82.45	$82.50
Purchase #3	$223.42	13.509%	$253.6018	$253.60	$253.60	$253.60
Purchase #4	$161.25	3.835%	$167.4339	$167.43	$167.45	$167.40
Purchase #5	$62.46	11.198%	$69.4543	$69.45	$69.45	$69.50
Purchase #6	$105.54	13.753%	$120.0549	$120.05	$120.05	$120.10
Purchase #7	$126.73	8.716%	$137.7758	$137.78	$137.80	$137.80
7 purchase totals =	$943.65		$1,043.6076	$1,043.59	$1,043.60	$1,043.70