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	$130.66	9.549%	$143.1367	$143.14	$143.15	$143.10
Purchase #2	$37.32	3.861%	$38.7609	$38.76	$38.75	$38.80
Purchase #3	$52.79	6.768%	$56.3628	$56.36	$56.35	$56.40
Purchase #4	$76.29	9.168%	$83.2843	$83.28	$83.30	$83.30
Purchase #5	$182.36	11.810%	$203.8967	$203.90	$203.90	$203.90
Purchase #6	$90.57	10.673%	$100.2365	$100.24	$100.25	$100.20
Purchase #7	$224.38	9.461%	$245.6086	$245.61	$245.60	$245.60
7 purchase totals =	$794.37		$871.2865	$871.29	$871.30	$871.30