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	$61.99	13.695%	$70.4795	$70.48	$70.50	$70.50
Purchase #2	$81.85	6.867%	$87.4706	$87.47	$87.45	$87.50
Purchase #3	$71.92	6.576%	$76.6495	$76.65	$76.65	$76.60
Purchase #4	$189.82	4.849%	$199.0244	$199.02	$199.00	$199.00
Purchase #5	$225.27	13.594%	$255.8932	$255.89	$255.90	$255.90
Purchase #6	$183.92	13.385%	$208.5377	$208.54	$208.55	$208.50
Purchase #7	$140.85	8.435%	$152.7307	$152.73	$152.75	$152.70
7 purchase totals =	$955.62		$1,050.7856	$1,050.78	$1,050.80	$1,050.70