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	$182.91	9.221%	$199.7761	$199.78	$199.80	$199.80
Purchase #2	$87.77	13.417%	$99.5461	$99.55	$99.55	$99.50
Purchase #3	$200.94	5.421%	$211.833	$211.83	$211.85	$211.80
Purchase #4	$169.59	3.834%	$176.0921	$176.09	$176.10	$176.10
Purchase #5	$220.93	10.742%	$244.6623	$244.66	$244.65	$244.70
Purchase #6	$60.56	3.215%	$62.507	$62.51	$62.50	$62.50
Purchase #7	$12.80	8.455%	$13.8822	$13.88	$13.90	$13.90
7 purchase totals =	$935.50		$1,008.2988	$1,008.30	$1,008.35	$1,008.30