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	$152.88	9.761%	$167.8026	$167.80	$167.80	$167.80
Purchase #2	$136.29	7.562%	$146.5962	$146.60	$146.60	$146.60
Purchase #3	$160.52	5.230%	$168.9152	$168.92	$168.90	$168.90
Purchase #4	$106.63	10.430%	$117.7515	$117.75	$117.75	$117.80
Purchase #5	$109.80	12.818%	$123.8742	$123.87	$123.85	$123.90
Purchase #6	$205.60	6.378%	$218.7132	$218.71	$218.70	$218.70
Purchase #7	$59.65	12.238%	$66.95	$66.95	$66.95	$67.00
7 purchase totals =	$931.37		$1,010.6029	$1,010.60	$1,010.55	$1,010.70