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	$168.55	8.285%	$182.5144	$182.51	$182.50	$182.50
Purchase #2	$154.38	5.385%	$162.6934	$162.69	$162.70	$162.70
Purchase #3	$9.49	11.765%	$10.6065	$10.61	$10.60	$10.60
Purchase #4	$42.47	3.652%	$44.021	$44.02	$44.00	$44.00
Purchase #5	$66.98	10.659%	$74.1194	$74.12	$74.10	$74.10
Purchase #6	$215.73	8.337%	$233.7154	$233.72	$233.70	$233.70
Purchase #7	$80.72	12.290%	$90.6405	$90.64	$90.65	$90.60
7 purchase totals =	$738.32		$798.3106	$798.31	$798.25	$798.20