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	$173.87	6.644%	$185.4219	$185.42	$185.40	$185.40
Purchase #2	$221.39	12.380%	$248.7981	$248.80	$248.80	$248.80
Purchase #3	$69.90	4.281%	$72.8924	$72.89	$72.90	$72.90
Purchase #4	$187.58	5.429%	$197.7637	$197.76	$197.75	$197.80
Purchase #5	$138.58	3.792%	$143.835	$143.84	$143.85	$143.80
Purchase #6	$100.82	5.580%	$106.4458	$106.45	$106.45	$106.40
Purchase #7	$29.59	8.734%	$32.1744	$32.17	$32.15	$32.20
7 purchase totals =	$921.73		$987.3313	$987.33	$987.30	$987.30