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	$175.66	5.593%	$185.4847	$185.48	$185.50	$185.50
Purchase #2	$180.49	6.706%	$192.5937	$192.59	$192.60	$192.60
Purchase #3	$88.97	12.406%	$100.0076	$100.01	$100.00	$100.00
Purchase #4	$88.26	7.720%	$95.0737	$95.07	$95.05	$95.10
Purchase #5	$137.51	9.204%	$150.1664	$150.17	$150.15	$150.20
Purchase #6	$105.88	13.465%	$120.1367	$120.14	$120.15	$120.10
Purchase #7	$72.45	6.121%	$76.8847	$76.88	$76.90	$76.90
7 purchase totals =	$849.22		$920.3475	$920.34	$920.35	$920.40