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	$138.30	6.633%	$147.4734	$147.47	$147.45	$147.50
Purchase #2	$50.88	5.181%	$53.5161	$53.52	$53.50	$53.50
Purchase #3	$128.90	13.594%	$146.4227	$146.42	$146.40	$146.40
Purchase #4	$95.93	9.858%	$105.3868	$105.39	$105.40	$105.40
Purchase #5	$102.74	11.587%	$114.6445	$114.64	$114.65	$114.60
Purchase #6	$215.45	7.709%	$232.059	$232.06	$232.05	$232.10
Purchase #7	$120.58	10.318%	$133.0214	$133.02	$133.00	$133.00
7 purchase totals =	$852.78		$932.5239	$932.52	$932.45	$932.50