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	$178.76	7.159%	$191.5574	$191.56	$191.55	$191.60
Purchase #2	$167.69	13.846%	$190.9084	$190.91	$190.90	$190.90
Purchase #3	$192.80	10.198%	$212.4617	$212.46	$212.45	$212.50
Purchase #4	$25.43	10.204%	$28.0249	$28.02	$28.00	$28.00
Purchase #5	$189.94	9.687%	$208.3395	$208.34	$208.35	$208.30
Purchase #6	$140.89	9.600%	$154.4154	$154.42	$154.40	$154.40
Purchase #7	$17.86	8.576%	$19.3917	$19.39	$19.40	$19.40
7 purchase totals =	$913.37		$1,005.0990	$1,005.10	$1,005.05	$1,005.10