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	$162.58	3.134%	$167.6753	$167.68	$167.70	$167.70
Purchase #2	$178.61	12.470%	$200.8827	$200.88	$200.90	$200.90
Purchase #3	$219.55	8.808%	$238.888	$238.89	$238.90	$238.90
Purchase #4	$70.92	7.460%	$76.2106	$76.21	$76.20	$76.20
Purchase #5	$144.54	7.637%	$155.5785	$155.58	$155.60	$155.60
Purchase #6	$160.62	5.416%	$169.3192	$169.32	$169.30	$169.30
Purchase #7	$32.35	4.644%	$33.8523	$33.85	$33.85	$33.90
7 purchase totals =	$969.17		$1,042.4066	$1,042.41	$1,042.45	$1,042.50