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	$169.35	9.401%	$185.2706	$185.27	$185.25	$185.30
Purchase #2	$193.43	5.174%	$203.4381	$203.44	$203.45	$203.40
Purchase #3	$139.39	4.686%	$145.9218	$145.92	$145.90	$145.90
Purchase #4	$140.47	4.871%	$147.3123	$147.31	$147.30	$147.30
Purchase #5	$85.78	5.631%	$90.6103	$90.61	$90.60	$90.60
Purchase #6	$160.56	11.856%	$179.596	$179.60	$179.60	$179.60
Purchase #7	$101.46	8.855%	$110.4443	$110.44	$110.45	$110.40
7 purchase totals =	$990.44		$1,062.5934	$1,062.59	$1,062.55	$1,062.50