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	$158.35	5.590%	$167.2018	$167.20	$167.20	$167.20
Purchase #2	$65.81	10.808%	$72.9227	$72.92	$72.90	$72.90
Purchase #3	$78.84	8.682%	$85.6849	$85.68	$85.70	$85.70
Purchase #4	$59.30	4.433%	$61.9288	$61.93	$61.95	$61.90
Purchase #5	$97.92	10.300%	$108.0058	$108.01	$108.00	$108.00
Purchase #6	$46.82	6.622%	$49.9204	$49.92	$49.90	$49.90
Purchase #7	$82.38	5.495%	$86.9068	$86.91	$86.90	$86.90
7 purchase totals =	$589.42		$632.5712	$632.57	$632.55	$632.50