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	$132.41	12.752%	$149.2949	$149.29	$149.30	$149.30
Purchase #2	$67.41	6.598%	$71.8577	$71.86	$71.85	$71.90
Purchase #3	$41.65	5.413%	$43.9045	$43.90	$43.90	$43.90
Purchase #4	$226.71	5.339%	$238.814	$238.81	$238.80	$238.80
Purchase #5	$117.86	5.771%	$124.6617	$124.66	$124.65	$124.70
Purchase #6	$195.59	4.330%	$204.059	$204.06	$204.05	$204.10
Purchase #7	$167.83	4.476%	$175.3421	$175.34	$175.35	$175.30
7 purchase totals =	$949.46		$1,007.9339	$1,007.92	$1,007.90	$1,008.00