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	$211.59	6.310%	$224.9413	$224.94	$224.95	$224.90
Purchase #2	$11.34	10.355%	$12.5143	$12.51	$12.50	$12.50
Purchase #3	$17.70	8.610%	$19.224	$19.22	$19.20	$19.20
Purchase #4	$92.92	7.866%	$100.2291	$100.23	$100.25	$100.20
Purchase #5	$43.64	8.280%	$47.2534	$47.25	$47.25	$47.30
Purchase #6	$71.42	9.800%	$78.4192	$78.42	$78.40	$78.40
Purchase #7	$216.27	5.380%	$227.9053	$227.91	$227.90	$227.90
7 purchase totals =	$664.88		$710.4866	$710.48	$710.45	$710.40