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	$141.66	10.794%	$156.9508	$156.95	$156.95	$157.00
Purchase #2	$152.72	13.835%	$173.8488	$173.85	$173.85	$173.80
Purchase #3	$37.34	13.570%	$42.407	$42.41	$42.40	$42.40
Purchase #4	$159.29	10.833%	$176.5459	$176.55	$176.55	$176.50
Purchase #5	$157.60	3.355%	$162.8875	$162.89	$162.90	$162.90
Purchase #6	$157.95	5.222%	$166.1981	$166.20	$166.20	$166.20
Purchase #7	$249.30	13.332%	$282.5367	$282.54	$282.55	$282.50
7 purchase totals =	$1,055.86		$1,161.3748	$1,161.39	$1,161.40	$1,161.30