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	$101.72	7.783%	$109.6369	$109.64	$109.65	$109.60
Purchase #2	$200.96	3.403%	$207.7987	$207.80	$207.80	$207.80
Purchase #3	$208.44	11.548%	$232.5107	$232.51	$232.50	$232.50
Purchase #4	$52.89	13.147%	$59.8434	$59.84	$59.85	$59.80
Purchase #5	$96.69	9.549%	$105.9229	$105.92	$105.90	$105.90
Purchase #6	$83.76	4.424%	$87.4655	$87.47	$87.45	$87.50
Purchase #7	$200.63	13.369%	$227.4522	$227.45	$227.45	$227.50
7 purchase totals =	$945.09		$1,030.6303	$1,030.63	$1,030.60	$1,030.60