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	$220.37	9.157%	$240.5493	$240.55	$240.55	$240.50
Purchase #2	$25.90	11.357%	$28.8415	$28.84	$28.85	$28.80
Purchase #3	$189.85	4.602%	$198.5869	$198.59	$198.60	$198.60
Purchase #4	$146.87	3.727%	$152.3438	$152.34	$152.35	$152.30
Purchase #5	$103.92	8.126%	$112.3645	$112.36	$112.35	$112.40
Purchase #6	$227.75	12.402%	$255.9956	$256.00	$256.00	$256.00
Purchase #7	$246.87	7.275%	$264.8298	$264.83	$264.85	$264.80
7 purchase totals =	$1,161.53		$1,253.5114	$1,253.51	$1,253.55	$1,253.40