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	$142.49	13.707%	$162.0211	$162.02	$162.00	$162.00
Purchase #2	$164.58	8.873%	$179.1832	$179.18	$179.20	$179.20
Purchase #3	$143.51	5.270%	$151.073	$151.07	$151.05	$151.10
Purchase #4	$86.54	9.709%	$94.9422	$94.94	$94.95	$94.90
Purchase #5	$90.90	13.678%	$103.3333	$103.33	$103.35	$103.30
Purchase #6	$87.54	13.501%	$99.3588	$99.36	$99.35	$99.40
Purchase #7	$9.50	4.576%	$9.9347	$9.93	$9.95	$9.90
7 purchase totals =	$725.06		$799.8463	$799.83	$799.85	$799.80