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	$176.49	3.614%	$182.8683	$182.87	$182.85	$182.90
Purchase #2	$180.56	9.768%	$198.1971	$198.20	$198.20	$198.20
Purchase #3	$80.25	4.245%	$83.6566	$83.66	$83.65	$83.70
Purchase #4	$42.89	8.442%	$46.5108	$46.51	$46.50	$46.50
Purchase #5	$174.48	9.815%	$191.6052	$191.61	$191.60	$191.60
Purchase #6	$55.38	11.563%	$61.7836	$61.78	$61.80	$61.80
Purchase #7	$131.94	3.181%	$136.137	$136.14	$136.15	$136.10
7 purchase totals =	$841.99		$900.7586	$900.77	$900.75	$900.80