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	$42.33	10.726%	$46.8703	$46.87	$46.85	$46.90
Purchase #2	$154.36	8.273%	$167.1302	$167.13	$167.15	$167.10
Purchase #3	$48.84	12.666%	$55.0261	$55.03	$55.05	$55.00
Purchase #4	$11.42	4.441%	$11.9272	$11.93	$11.95	$11.90
Purchase #5	$65.86	10.261%	$72.6179	$72.62	$72.60	$72.60
Purchase #6	$26.72	12.669%	$30.1052	$30.11	$30.10	$30.10
Purchase #7	$119.63	6.534%	$127.4466	$127.45	$127.45	$127.40
7 purchase totals =	$469.16		$511.1235	$511.14	$511.15	$511.00