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	$151.31	11.428%	$168.6017	$168.60	$168.60	$168.60
Purchase #2	$162.88	5.835%	$172.384	$172.38	$172.40	$172.40
Purchase #3	$248.82	9.313%	$271.9926	$271.99	$272.00	$272.00
Purchase #4	$205.35	7.637%	$221.0326	$221.03	$221.05	$221.00
Purchase #5	$191.44	11.470%	$213.3982	$213.40	$213.40	$213.40
Purchase #6	$34.90	11.187%	$38.8043	$38.80	$38.80	$38.80
Purchase #7	$52.78	13.587%	$59.9512	$59.95	$59.95	$60.00
7 purchase totals =	$1,047.48		$1,146.1646	$1,146.15	$1,146.20	$1,146.20