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	$147.65	8.526%	$160.2386	$160.24	$160.25	$160.20
Purchase #2	$114.36	8.315%	$123.869	$123.87	$123.85	$123.90
Purchase #3	$156.31	6.444%	$166.3826	$166.38	$166.40	$166.40
Purchase #4	$211.50	5.222%	$222.5445	$222.54	$222.55	$222.50
Purchase #5	$241.94	8.461%	$262.4105	$262.41	$262.40	$262.40
Purchase #6	$26.70	4.395%	$27.8735	$27.87	$27.85	$27.90
Purchase #7	$192.28	12.464%	$216.2458	$216.25	$216.25	$216.20
7 purchase totals =	$1,090.74		$1,179.5645	$1,179.56	$1,179.55	$1,179.50