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	$87.75	6.301%	$93.2791	$93.28	$93.30	$93.30
Purchase #2	$208.99	7.827%	$225.3476	$225.35	$225.35	$225.30
Purchase #3	$190.65	13.545%	$216.4735	$216.47	$216.45	$216.50
Purchase #4	$207.96	13.435%	$235.8994	$235.90	$235.90	$235.90
Purchase #5	$87.31	3.459%	$90.3301	$90.33	$90.35	$90.30
Purchase #6	$132.59	9.300%	$144.9209	$144.92	$144.90	$144.90
Purchase #7	$22.36	8.730%	$24.312	$24.31	$24.30	$24.30
7 purchase totals =	$937.61		$1,030.5626	$1,030.56	$1,030.55	$1,030.50