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	$199.59	4.449%	$208.4698	$208.47	$208.45	$208.50
Purchase #2	$185.54	13.674%	$210.9107	$210.91	$210.90	$210.90
Purchase #3	$243.78	5.760%	$257.8217	$257.82	$257.80	$257.80
Purchase #4	$85.30	11.849%	$95.4072	$95.41	$95.40	$95.40
Purchase #5	$84.25	3.193%	$86.9401	$86.94	$86.95	$86.90
Purchase #6	$155.83	6.386%	$165.7813	$165.78	$165.80	$165.80
Purchase #7	$49.88	10.805%	$55.2695	$55.27	$55.25	$55.30
7 purchase totals =	$1,004.17		$1,080.6003	$1,080.60	$1,080.55	$1,080.60