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	$14.73	9.802%	$16.1738	$16.17	$16.15	$16.20
Purchase #2	$248.59	8.768%	$270.3864	$270.39	$270.40	$270.40
Purchase #3	$126.83	10.345%	$139.9506	$139.95	$139.95	$140.00
Purchase #4	$232.51	10.510%	$256.9468	$256.95	$256.95	$256.90
Purchase #5	$68.86	5.451%	$72.6136	$72.61	$72.60	$72.60
Purchase #6	$77.48	5.639%	$81.8491	$81.85	$81.85	$81.80
Purchase #7	$245.43	3.839%	$254.8521	$254.85	$254.85	$254.90
7 purchase totals =	$1,014.43		$1,092.7724	$1,092.77	$1,092.75	$1,092.80