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	$208.49	9.278%	$227.8337	$227.83	$227.85	$227.80
Purchase #2	$238.96	7.349%	$256.5212	$256.52	$256.50	$256.50
Purchase #3	$223.54	12.492%	$251.4646	$251.46	$251.45	$251.50
Purchase #4	$79.78	7.132%	$85.4699	$85.47	$85.45	$85.50
Purchase #5	$186.26	4.638%	$194.8987	$194.90	$194.90	$194.90
Purchase #6	$145.40	12.789%	$163.9952	$164.00	$164.00	$164.00
Purchase #7	$79.25	13.474%	$89.9281	$89.93	$89.95	$89.90
7 purchase totals =	$1,161.68		$1,270.1114	$1,270.11	$1,270.10	$1,270.10