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	$126.68	4.106%	$131.8815	$131.88	$131.90	$131.90
Purchase #2	$186.27	5.487%	$196.4906	$196.49	$196.50	$196.50
Purchase #3	$128.89	3.274%	$133.1099	$133.11	$133.10	$133.10
Purchase #4	$250.91	6.282%	$266.6722	$266.67	$266.65	$266.70
Purchase #5	$102.79	13.541%	$116.7088	$116.71	$116.70	$116.70
Purchase #6	$115.61	7.274%	$124.0195	$124.02	$124.00	$124.00
Purchase #7	$25.90	6.526%	$27.5902	$27.59	$27.60	$27.60
7 purchase totals =	$937.05		$996.4727	$996.47	$996.45	$996.50