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	$133.62	4.284%	$139.3443	$139.34	$139.35	$139.30
Purchase #2	$48.57	8.360%	$52.6305	$52.63	$52.65	$52.60
Purchase #3	$234.75	5.257%	$247.0908	$247.09	$247.10	$247.10
Purchase #4	$173.38	13.130%	$196.1448	$196.14	$196.15	$196.10
Purchase #5	$88.43	13.466%	$100.338	$100.34	$100.35	$100.30
Purchase #6	$221.55	4.679%	$231.9163	$231.92	$231.90	$231.90
Purchase #7	$52.97	11.488%	$59.0552	$59.06	$59.05	$59.10
7 purchase totals =	$953.27		$1,026.5199	$1,026.52	$1,026.55	$1,026.40