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	$140.63	9.408%	$153.8605	$153.86	$153.85	$153.90
Purchase #2	$204.59	8.755%	$222.5019	$222.50	$222.50	$222.50
Purchase #3	$243.38	6.643%	$259.5477	$259.55	$259.55	$259.50
Purchase #4	$103.63	8.200%	$112.1277	$112.13	$112.15	$112.10
Purchase #5	$209.56	11.683%	$234.0429	$234.04	$234.05	$234.00
Purchase #6	$87.96	3.300%	$90.8627	$90.86	$90.85	$90.90
Purchase #7	$54.46	11.113%	$60.5121	$60.51	$60.50	$60.50
7 purchase totals =	$1,044.21		$1,133.4555	$1,133.45	$1,133.45	$1,133.40