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	$164.56	8.687%	$178.8553	$178.86	$178.85	$178.90
Purchase #2	$127.60	7.186%	$136.7693	$136.77	$136.75	$136.80
Purchase #3	$200.54	11.166%	$222.9323	$222.93	$222.95	$222.90
Purchase #4	$7.34	7.110%	$7.8619	$7.86	$7.85	$7.90
Purchase #5	$113.60	11.139%	$126.2539	$126.25	$126.25	$126.30
Purchase #6	$83.94	4.272%	$87.5259	$87.53	$87.55	$87.50
Purchase #7	$42.30	4.439%	$44.1777	$44.18	$44.20	$44.20
7 purchase totals =	$739.88		$804.3763	$804.38	$804.40	$804.50