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	$88.46	4.683%	$92.6026	$92.60	$92.60	$92.60
Purchase #2	$104.37	9.479%	$114.2632	$114.26	$114.25	$114.30
Purchase #3	$112.57	5.615%	$118.8908	$118.89	$118.90	$118.90
Purchase #4	$72.48	11.240%	$80.6268	$80.63	$80.65	$80.60
Purchase #5	$57.63	3.598%	$59.7035	$59.70	$59.70	$59.70
Purchase #6	$158.34	4.174%	$164.9491	$164.95	$164.95	$164.90
Purchase #7	$84.85	8.300%	$91.8926	$91.89	$91.90	$91.90
7 purchase totals =	$678.70		$722.9286	$722.92	$722.95	$722.90