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	$218.95	6.686%	$233.589	$233.59	$233.60	$233.60
Purchase #2	$219.32	13.513%	$248.9567	$248.96	$248.95	$249.00
Purchase #3	$192.56	7.764%	$207.5104	$207.51	$207.50	$207.50
Purchase #4	$107.69	3.142%	$111.0736	$111.07	$111.05	$111.10
Purchase #5	$24.68	11.772%	$27.5853	$27.59	$27.60	$27.60
Purchase #6	$241.61	13.215%	$273.5388	$273.54	$273.55	$273.50
Purchase #7	$87.54	4.796%	$91.7384	$91.74	$91.75	$91.70
7 purchase totals =	$1,092.35		$1,193.9922	$1,194.00	$1,194.00	$1,194.00