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	$182.29	12.465%	$205.0124	$205.01	$205.00	$205.00
Purchase #2	$92.53	3.311%	$95.5937	$95.59	$95.60	$95.60
Purchase #3	$61.30	7.570%	$65.9404	$65.94	$65.95	$65.90
Purchase #4	$227.59	9.102%	$248.3052	$248.31	$248.30	$248.30
Purchase #5	$241.41	11.813%	$269.9278	$269.93	$269.95	$269.90
Purchase #6	$86.55	3.794%	$89.8337	$89.83	$89.85	$89.80
Purchase #7	$12.63	9.520%	$13.8324	$13.83	$13.85	$13.80
7 purchase totals =	$904.30		$988.4456	$988.44	$988.50	$988.30