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	$207.36	4.403%	$216.4901	$216.49	$216.50	$216.50
Purchase #2	$87.53	13.247%	$99.1251	$99.13	$99.15	$99.10
Purchase #3	$52.29	13.571%	$59.3863	$59.39	$59.40	$59.40
Purchase #4	$107.44	7.218%	$115.195	$115.20	$115.20	$115.20
Purchase #5	$201.49	7.636%	$216.8758	$216.88	$216.90	$216.90
Purchase #6	$69.51	4.349%	$72.533	$72.53	$72.55	$72.50
Purchase #7	$68.53	4.845%	$71.8503	$71.85	$71.85	$71.90
7 purchase totals =	$794.15		$851.4556	$851.47	$851.55	$851.50