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	$132.51	7.106%	$141.9262	$141.93	$141.95	$141.90
Purchase #2	$28.91	13.668%	$32.8614	$32.86	$32.85	$32.90
Purchase #3	$246.79	8.841%	$268.6087	$268.61	$268.60	$268.60
Purchase #4	$154.95	6.797%	$165.482	$165.48	$165.50	$165.50
Purchase #5	$140.61	3.760%	$145.8969	$145.90	$145.90	$145.90
Purchase #6	$227.43	12.131%	$255.0195	$255.02	$255.00	$255.00
Purchase #7	$106.95	9.830%	$117.4632	$117.46	$117.45	$117.50
7 purchase totals =	$1,038.15		$1,127.2579	$1,127.26	$1,127.25	$1,127.30