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	$243.30	5.487%	$256.6499	$256.65	$256.65	$256.60
Purchase #2	$26.70	10.178%	$29.4175	$29.42	$29.40	$29.40
Purchase #3	$164.48	9.369%	$179.8901	$179.89	$179.90	$179.90
Purchase #4	$56.36	5.542%	$59.4835	$59.48	$59.50	$59.50
Purchase #5	$234.78	4.157%	$244.5398	$244.54	$244.55	$244.50
Purchase #6	$169.52	6.521%	$180.5744	$180.57	$180.55	$180.60
Purchase #7	$94.78	7.496%	$101.8847	$101.88	$101.90	$101.90
7 purchase totals =	$989.92		$1,052.4399	$1,052.43	$1,052.45	$1,052.40