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	$231.39	6.204%	$245.7454	$245.75	$245.75	$245.70
Purchase #2	$52.54	3.602%	$54.4325	$54.43	$54.45	$54.40
Purchase #3	$193.79	3.370%	$200.3207	$200.32	$200.30	$200.30
Purchase #4	$213.55	12.696%	$240.6623	$240.66	$240.65	$240.70
Purchase #5	$166.52	10.520%	$184.0379	$184.04	$184.05	$184.00
Purchase #6	$78.72	8.507%	$85.4167	$85.42	$85.40	$85.40
Purchase #7	$16.65	10.806%	$18.4492	$18.45	$18.45	$18.40
7 purchase totals =	$953.16		$1,029.0647	$1,029.07	$1,029.05	$1,028.90