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	$113.52	13.128%	$128.4229	$128.42	$128.40	$128.40
Purchase #2	$176.44	11.349%	$196.4642	$196.46	$196.45	$196.50
Purchase #3	$238.51	9.704%	$261.655	$261.66	$261.65	$261.70
Purchase #4	$90.76	5.615%	$95.8562	$95.86	$95.85	$95.90
Purchase #5	$234.72	4.193%	$244.5618	$244.56	$244.55	$244.60
Purchase #6	$184.38	3.155%	$190.1972	$190.20	$190.20	$190.20
Purchase #7	$12.25	9.505%	$13.4144	$13.41	$13.40	$13.40
7 purchase totals =	$1,050.58		$1,130.5717	$1,130.57	$1,130.50	$1,130.70