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	$97.39	6.323%	$103.548	$103.55	$103.55	$103.50
Purchase #2	$208.46	9.284%	$227.8134	$227.81	$227.80	$227.80
Purchase #3	$100.74	7.272%	$108.0658	$108.07	$108.05	$108.10
Purchase #4	$138.97	6.768%	$148.3755	$148.38	$148.40	$148.40
Purchase #5	$174.31	9.479%	$190.8328	$190.83	$190.85	$190.80
Purchase #6	$140.64	7.113%	$150.6437	$150.64	$150.65	$150.60
Purchase #7	$84.54	11.583%	$94.3323	$94.33	$94.35	$94.30
7 purchase totals =	$945.05		$1,023.6115	$1,023.61	$1,023.65	$1,023.50