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	$102.72	3.150%	$105.9557	$105.96	$105.95	$106.00
Purchase #2	$116.95	6.386%	$124.4184	$124.42	$124.40	$124.40
Purchase #3	$127.78	6.316%	$135.8506	$135.85	$135.85	$135.90
Purchase #4	$74.38	5.515%	$78.4821	$78.48	$78.50	$78.50
Purchase #5	$39.66	9.249%	$43.3282	$43.33	$43.35	$43.30
Purchase #6	$175.61	7.333%	$188.4875	$188.49	$188.50	$188.50
Purchase #7	$184.79	11.372%	$205.8043	$205.80	$205.80	$205.80
7 purchase totals =	$821.89		$882.3268	$882.33	$882.35	$882.40