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	$119.77	9.305%	$130.9146	$130.91	$130.90	$130.90
Purchase #2	$199.57	6.172%	$211.8875	$211.89	$211.90	$211.90
Purchase #3	$136.90	5.229%	$144.0585	$144.06	$144.05	$144.10
Purchase #4	$75.91	9.763%	$83.3211	$83.32	$83.30	$83.30
Purchase #5	$220.70	11.850%	$246.853	$246.85	$246.85	$246.90
Purchase #6	$93.33	6.622%	$99.5103	$99.51	$99.50	$99.50
Purchase #7	$21.80	13.202%	$24.678	$24.68	$24.70	$24.70
7 purchase totals =	$867.98		$941.2230	$941.22	$941.20	$941.30