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	$101.85	6.280%	$108.2462	$108.25	$108.25	$108.20
Purchase #2	$151.34	11.427%	$168.6336	$168.63	$168.65	$168.60
Purchase #3	$250.30	4.577%	$261.7562	$261.76	$261.75	$261.80
Purchase #4	$131.59	7.273%	$141.1605	$141.16	$141.15	$141.20
Purchase #5	$142.81	13.586%	$162.2122	$162.21	$162.20	$162.20
Purchase #6	$19.48	7.140%	$20.8709	$20.87	$20.85	$20.90
Purchase #7	$27.80	13.707%	$31.6105	$31.61	$31.60	$31.60
7 purchase totals =	$825.17		$894.4901	$894.49	$894.45	$894.50