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	$85.92	12.647%	$96.7863	$96.79	$96.80	$96.80
Purchase #2	$210.53	6.579%	$224.3808	$224.38	$224.40	$224.40
Purchase #3	$123.97	7.193%	$132.8872	$132.89	$132.90	$132.90
Purchase #4	$94.35	5.729%	$99.7553	$99.76	$99.75	$99.80
Purchase #5	$72.79	7.801%	$78.4683	$78.47	$78.45	$78.50
Purchase #6	$146.85	3.602%	$152.1395	$152.14	$152.15	$152.10
Purchase #7	$200.56	6.805%	$214.2081	$214.21	$214.20	$214.20
7 purchase totals =	$934.97		$998.6255	$998.64	$998.65	$998.70