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	$147.83	10.369%	$163.1585	$163.16	$163.15	$163.20
Purchase #2	$114.89	10.293%	$126.7156	$126.72	$126.70	$126.70
Purchase #3	$28.67	12.299%	$32.1961	$32.20	$32.20	$32.20
Purchase #4	$56.90	7.132%	$60.9581	$60.96	$60.95	$61.00
Purchase #5	$178.64	3.178%	$184.3172	$184.32	$184.30	$184.30
Purchase #6	$117.90	11.849%	$131.87	$131.87	$131.85	$131.90
Purchase #7	$248.98	12.106%	$279.1215	$279.12	$279.10	$279.10
7 purchase totals =	$893.81		$978.3370	$978.35	$978.25	$978.40