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	$211.35	5.689%	$223.3737	$223.37	$223.35	$223.40
Purchase #2	$87.25	3.367%	$90.1877	$90.19	$90.20	$90.20
Purchase #3	$45.65	7.141%	$48.9099	$48.91	$48.90	$48.90
Purchase #4	$172.43	7.479%	$185.326	$185.33	$185.35	$185.30
Purchase #5	$225.98	13.269%	$255.9653	$255.97	$255.95	$256.00
Purchase #6	$119.54	4.800%	$125.2779	$125.28	$125.30	$125.30
Purchase #7	$156.30	7.496%	$168.0162	$168.02	$168.00	$168.00
7 purchase totals =	$1,018.50		$1,097.0567	$1,097.07	$1,097.05	$1,097.10