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	$14.96	13.814%	$17.0266	$17.03	$17.05	$17.00
Purchase #2	$137.34	10.860%	$152.2551	$152.26	$152.25	$152.30
Purchase #3	$117.43	12.279%	$131.8492	$131.85	$131.85	$131.80
Purchase #4	$83.73	8.612%	$90.9408	$90.94	$90.95	$90.90
Purchase #5	$160.65	11.477%	$179.0878	$179.09	$179.10	$179.10
Purchase #6	$78.61	8.378%	$85.1959	$85.20	$85.20	$85.20
Purchase #7	$233.46	4.180%	$243.2186	$243.22	$243.20	$243.20
7 purchase totals =	$826.18		$899.5740	$899.59	$899.60	$899.50