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	$86.54	7.382%	$92.9284	$92.93	$92.95	$92.90
Purchase #2	$123.73	6.120%	$131.3023	$131.30	$131.30	$131.30
Purchase #3	$186.54	4.493%	$194.9212	$194.92	$194.90	$194.90
Purchase #4	$186.77	5.440%	$196.9303	$196.93	$196.95	$196.90
Purchase #5	$29.98	12.677%	$33.7806	$33.78	$33.80	$33.80
Purchase #6	$70.68	8.418%	$76.6298	$76.63	$76.65	$76.60
Purchase #7	$59.92	8.167%	$64.8137	$64.81	$64.80	$64.80
7 purchase totals =	$744.16		$791.3063	$791.30	$791.35	$791.20