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	$171.86	12.337%	$193.0624	$193.06	$193.05	$193.10
Purchase #2	$60.47	5.666%	$63.8962	$63.90	$63.90	$63.90
Purchase #3	$124.85	12.833%	$140.872	$140.87	$140.85	$140.90
Purchase #4	$37.55	8.829%	$40.8653	$40.87	$40.85	$40.90
Purchase #5	$230.64	5.382%	$243.053	$243.05	$243.05	$243.10
Purchase #6	$201.89	10.381%	$222.8482	$222.85	$222.85	$222.80
Purchase #7	$107.59	6.275%	$114.3413	$114.34	$114.35	$114.30
7 purchase totals =	$934.85		$1,018.9384	$1,018.94	$1,018.90	$1,019.00