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	$64.46	11.503%	$71.8748	$71.87	$71.85	$71.90
Purchase #2	$27.25	9.227%	$29.7644	$29.76	$29.75	$29.80
Purchase #3	$30.62	12.700%	$34.5087	$34.51	$34.50	$34.50
Purchase #4	$21.39	5.751%	$22.6201	$22.62	$22.60	$22.60
Purchase #5	$55.41	13.269%	$62.7624	$62.76	$62.75	$62.80
Purchase #6	$76.26	8.287%	$82.5797	$82.58	$82.60	$82.60
Purchase #7	$103.34	3.596%	$107.0561	$107.06	$107.05	$107.10
7 purchase totals =	$378.73		$411.1662	$411.16	$411.10	$411.30