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	$101.37	10.359%	$111.8709	$111.87	$111.85	$111.90
Purchase #2	$78.38	7.382%	$84.166	$84.17	$84.15	$84.20
Purchase #3	$187.66	7.151%	$201.0796	$201.08	$201.10	$201.10
Purchase #4	$115.33	13.315%	$130.6862	$130.69	$130.70	$130.70
Purchase #5	$248.68	11.491%	$277.2558	$277.26	$277.25	$277.30
Purchase #6	$125.59	12.638%	$141.4621	$141.46	$141.45	$141.50
Purchase #7	$72.86	8.223%	$78.8513	$78.85	$78.85	$78.90
7 purchase totals =	$929.87		$1,025.3719	$1,025.38	$1,025.35	$1,025.60