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	$106.52	7.439%	$114.444	$114.44	$114.45	$114.40
Purchase #2	$18.66	11.268%	$20.7626	$20.76	$20.75	$20.80
Purchase #3	$232.91	11.136%	$258.8469	$258.85	$258.85	$258.80
Purchase #4	$113.51	8.576%	$123.2446	$123.24	$123.25	$123.20
Purchase #5	$85.45	10.431%	$94.3633	$94.36	$94.35	$94.40
Purchase #6	$36.69	3.522%	$37.9822	$37.98	$38.00	$38.00
Purchase #7	$123.90	6.390%	$131.8172	$131.82	$131.80	$131.80
7 purchase totals =	$717.64		$781.4608	$781.45	$781.45	$781.40