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	$227.53	13.863%	$259.0725	$259.07	$259.05	$259.10
Purchase #2	$51.48	9.535%	$56.3886	$56.39	$56.40	$56.40
Purchase #3	$46.38	8.527%	$50.3348	$50.33	$50.35	$50.30
Purchase #4	$221.65	12.810%	$250.0434	$250.04	$250.05	$250.00
Purchase #5	$179.89	4.382%	$187.7728	$187.77	$187.75	$187.80
Purchase #6	$57.76	6.152%	$61.3134	$61.31	$61.30	$61.30
Purchase #7	$189.73	3.790%	$196.9208	$196.92	$196.90	$196.90
7 purchase totals =	$974.42		$1,061.8463	$1,061.83	$1,061.80	$1,061.80