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	$88.38	5.179%	$92.9572	$92.96	$92.95	$93.00
Purchase #2	$68.54	11.495%	$76.4187	$76.42	$76.40	$76.40
Purchase #3	$73.53	6.873%	$78.5837	$78.58	$78.60	$78.60
Purchase #4	$13.96	7.588%	$15.0193	$15.02	$15.00	$15.00
Purchase #5	$51.53	8.804%	$56.0667	$56.07	$56.05	$56.10
Purchase #6	$136.67	3.786%	$141.8443	$141.84	$141.85	$141.80
Purchase #7	$92.87	11.503%	$103.5528	$103.55	$103.55	$103.60
7 purchase totals =	$525.48		$564.4427	$564.44	$564.40	$564.50