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	$208.83	3.364%	$215.855	$215.86	$215.85	$215.90
Purchase #2	$103.76	13.586%	$117.8568	$117.86	$117.85	$117.90
Purchase #3	$84.55	5.241%	$88.9813	$88.98	$89.00	$89.00
Purchase #4	$162.37	7.357%	$174.3156	$174.32	$174.30	$174.30
Purchase #5	$52.72	12.571%	$59.3474	$59.35	$59.35	$59.30
Purchase #6	$65.32	3.791%	$67.7963	$67.80	$67.80	$67.80
Purchase #7	$85.72	8.222%	$92.7679	$92.77	$92.75	$92.80
7 purchase totals =	$763.27		$816.9203	$816.94	$816.90	$817.00