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	$127.97	9.211%	$139.7573	$139.76	$139.75	$139.80
Purchase #2	$142.39	6.724%	$151.9643	$151.96	$151.95	$152.00
Purchase #3	$234.36	13.452%	$265.8861	$265.89	$265.90	$265.90
Purchase #4	$144.58	5.574%	$152.6389	$152.64	$152.65	$152.60
Purchase #5	$38.86	3.574%	$40.2489	$40.25	$40.25	$40.20
Purchase #6	$231.92	3.858%	$240.8675	$240.87	$240.85	$240.90
Purchase #7	$143.28	13.211%	$162.2087	$162.21	$162.20	$162.20
7 purchase totals =	$1,063.36		$1,153.5717	$1,153.58	$1,153.55	$1,153.60