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	$208.31	4.685%	$218.0693	$218.07	$218.05	$218.10
Purchase #2	$79.42	11.799%	$88.7908	$88.79	$88.80	$88.80
Purchase #3	$98.29	5.667%	$103.8601	$103.86	$103.85	$103.90
Purchase #4	$125.76	12.428%	$141.3895	$141.39	$141.40	$141.40
Purchase #5	$138.43	3.548%	$143.3415	$143.34	$143.35	$143.30
Purchase #6	$130.83	8.438%	$141.8694	$141.87	$141.85	$141.90
Purchase #7	$242.49	13.622%	$275.522	$275.52	$275.50	$275.50
7 purchase totals =	$1,023.53		$1,112.8426	$1,112.84	$1,112.80	$1,112.90