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	$149.70	11.162%	$166.4095	$166.41	$166.40	$166.40
Purchase #2	$132.84	3.366%	$137.3114	$137.31	$137.30	$137.30
Purchase #3	$14.34	6.756%	$15.3088	$15.31	$15.30	$15.30
Purchase #4	$81.99	10.864%	$90.8974	$90.90	$90.90	$90.90
Purchase #5	$65.71	6.561%	$70.0212	$70.02	$70.00	$70.00
Purchase #6	$130.96	12.556%	$147.4033	$147.40	$147.40	$147.40
Purchase #7	$101.51	7.582%	$109.2065	$109.21	$109.20	$109.20
7 purchase totals =	$677.05		$736.5581	$736.56	$736.50	$736.50