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	$116.36	5.740%	$123.0391	$123.04	$123.05	$123.00
Purchase #2	$181.38	9.638%	$198.8614	$198.86	$198.85	$198.90
Purchase #3	$189.56	8.107%	$204.9276	$204.93	$204.95	$204.90
Purchase #4	$52.89	12.843%	$59.6827	$59.68	$59.70	$59.70
Purchase #5	$88.35	9.109%	$96.3978	$96.40	$96.40	$96.40
Purchase #6	$9.51	10.153%	$10.4756	$10.48	$10.50	$10.50
Purchase #7	$231.52	13.575%	$262.9488	$262.95	$262.95	$262.90
7 purchase totals =	$869.57		$956.3330	$956.34	$956.40	$956.30