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	$146.79	7.683%	$158.0679	$158.07	$158.05	$158.10
Purchase #2	$195.79	10.790%	$216.9157	$216.92	$216.90	$216.90
Purchase #3	$42.28	10.847%	$46.8661	$46.87	$46.85	$46.90
Purchase #4	$84.36	7.805%	$90.9443	$90.94	$90.95	$90.90
Purchase #5	$69.38	6.417%	$73.8321	$73.83	$73.85	$73.80
Purchase #6	$38.88	11.435%	$43.3259	$43.33	$43.35	$43.30
Purchase #7	$85.66	5.126%	$90.0509	$90.05	$90.05	$90.10
7 purchase totals =	$663.14		$720.0029	$720.01	$720.00	$720.00