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	$33.97	10.367%	$37.4917	$37.49	$37.50	$37.50
Purchase #2	$47.89	13.748%	$54.4739	$54.47	$54.45	$54.50
Purchase #3	$168.32	3.800%	$174.7162	$174.72	$174.70	$174.70
Purchase #4	$192.88	10.149%	$212.4554	$212.46	$212.45	$212.50
Purchase #5	$212.59	5.567%	$224.4249	$224.42	$224.40	$224.40
Purchase #6	$128.53	8.511%	$139.4692	$139.47	$139.45	$139.50
Purchase #7	$90.39	9.150%	$98.6607	$98.66	$98.65	$98.70
7 purchase totals =	$874.57		$941.6920	$941.69	$941.60	$941.80