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	$76.47	13.315%	$86.652	$86.65	$86.65	$86.70
Purchase #2	$77.70	5.318%	$81.8321	$81.83	$81.85	$81.80
Purchase #3	$64.87	11.741%	$72.4864	$72.49	$72.50	$72.50
Purchase #4	$223.52	9.562%	$244.893	$244.89	$244.90	$244.90
Purchase #5	$44.62	7.406%	$47.9246	$47.92	$47.90	$47.90
Purchase #6	$74.33	11.162%	$82.6267	$82.63	$82.65	$82.60
Purchase #7	$200.41	10.575%	$221.6034	$221.60	$221.60	$221.60
7 purchase totals =	$761.92		$838.0182	$838.01	$838.05	$838.00