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	$152.43	8.349%	$165.1564	$165.16	$165.15	$165.20
Purchase #2	$62.45	3.438%	$64.597	$64.60	$64.60	$64.60
Purchase #3	$35.88	8.546%	$38.9463	$38.95	$38.95	$38.90
Purchase #4	$248.34	10.511%	$274.443	$274.44	$274.45	$274.40
Purchase #5	$167.54	6.162%	$177.8638	$177.86	$177.85	$177.90
Purchase #6	$57.28	4.644%	$59.9401	$59.94	$59.95	$59.90
Purchase #7	$171.63	9.675%	$188.2352	$188.24	$188.25	$188.20
7 purchase totals =	$895.55		$969.1818	$969.19	$969.20	$969.10