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	$179.38	3.602%	$185.8413	$185.84	$185.85	$185.80
Purchase #2	$179.53	11.402%	$200	$200.00	$200.00	$200.00
Purchase #3	$154.53	11.807%	$172.7754	$172.78	$172.80	$172.80
Purchase #4	$113.58	8.705%	$123.4671	$123.47	$123.45	$123.50
Purchase #5	$249.64	13.866%	$284.2551	$284.26	$284.25	$284.30
Purchase #6	$59.79	13.547%	$67.8898	$67.89	$67.90	$67.90
Purchase #7	$190.93	10.348%	$210.6874	$210.69	$210.70	$210.70
7 purchase totals =	$1,127.38		$1,244.9161	$1,244.93	$1,244.95	$1,245.00