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	$128.45	10.482%	$141.9141	$141.91	$141.90	$141.90
Purchase #2	$46.52	5.560%	$49.1065	$49.11	$49.10	$49.10
Purchase #3	$55.97	6.228%	$59.4558	$59.46	$59.45	$59.50
Purchase #4	$156.30	9.672%	$171.4173	$171.42	$171.40	$171.40
Purchase #5	$99.85	8.723%	$108.5599	$108.56	$108.55	$108.60
Purchase #6	$189.47	5.534%	$199.9553	$199.96	$199.95	$200.00
Purchase #7	$68.40	11.204%	$76.0635	$76.06	$76.05	$76.10
7 purchase totals =	$744.96		$806.4724	$806.48	$806.40	$806.60