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	$152.59	3.813%	$158.4083	$158.41	$158.40	$158.40
Purchase #2	$20.26	10.409%	$22.3689	$22.37	$22.35	$22.40
Purchase #3	$199.78	9.445%	$218.6492	$218.65	$218.65	$218.60
Purchase #4	$141.62	10.515%	$156.5113	$156.51	$156.50	$156.50
Purchase #5	$159.65	8.249%	$172.8195	$172.82	$172.80	$172.80
Purchase #6	$81.33	9.330%	$88.9181	$88.92	$88.90	$88.90
Purchase #7	$206.43	12.221%	$231.6578	$231.66	$231.65	$231.70
7 purchase totals =	$961.66		$1,049.3331	$1,049.34	$1,049.25	$1,049.30