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	$196.86	10.217%	$216.9732	$216.97	$216.95	$217.00
Purchase #2	$13.55	13.191%	$15.3374	$15.34	$15.35	$15.30
Purchase #3	$156.83	3.278%	$161.9709	$161.97	$161.95	$162.00
Purchase #4	$70.53	11.404%	$78.5732	$78.57	$78.55	$78.60
Purchase #5	$123.51	13.280%	$139.9121	$139.91	$139.90	$139.90
Purchase #6	$142.50	5.365%	$150.1451	$150.15	$150.15	$150.10
Purchase #7	$114.59	8.805%	$124.6796	$124.68	$124.70	$124.70
7 purchase totals =	$818.37		$887.5915	$887.59	$887.55	$887.60