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	$181.99	8.840%	$198.0779	$198.08	$198.10	$198.10
Purchase #2	$209.31	6.269%	$222.4316	$222.43	$222.45	$222.40
Purchase #3	$112.36	13.874%	$127.9488	$127.95	$127.95	$127.90
Purchase #4	$35.96	11.141%	$39.9663	$39.97	$39.95	$40.00
Purchase #5	$127.50	3.209%	$131.5915	$131.59	$131.60	$131.60
Purchase #6	$227.39	7.191%	$243.7416	$243.74	$243.75	$243.70
Purchase #7	$217.35	6.393%	$231.2452	$231.25	$231.25	$231.20
7 purchase totals =	$1,111.86		$1,195.0029	$1,195.01	$1,195.05	$1,194.90