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	$250.41	9.497%	$274.1914	$274.19	$274.20	$274.20
Purchase #2	$244.44	7.169%	$261.9639	$261.96	$261.95	$262.00
Purchase #3	$92.25	3.153%	$95.1586	$95.16	$95.15	$95.20
Purchase #4	$124.82	12.796%	$140.792	$140.79	$140.80	$140.80
Purchase #5	$220.42	13.657%	$250.5228	$250.52	$250.50	$250.50
Purchase #6	$100.35	11.703%	$112.094	$112.09	$112.10	$112.10
Purchase #7	$59.37	10.440%	$65.5682	$65.57	$65.55	$65.60
7 purchase totals =	$1,092.06		$1,200.2909	$1,200.28	$1,200.25	$1,200.40