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	$66.82	4.269%	$69.6725	$69.67	$69.65	$69.70
Purchase #2	$206.46	4.188%	$215.1065	$215.11	$215.10	$215.10
Purchase #3	$52.29	13.224%	$59.2048	$59.20	$59.20	$59.20
Purchase #4	$164.83	11.208%	$183.3041	$183.30	$183.30	$183.30
Purchase #5	$164.34	10.347%	$181.3443	$181.34	$181.35	$181.30
Purchase #6	$173.76	7.699%	$187.1378	$187.14	$187.15	$187.10
Purchase #7	$37.91	7.320%	$40.685	$40.69	$40.70	$40.70
7 purchase totals =	$866.41		$936.4550	$936.45	$936.45	$936.40