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	$222.89	4.598%	$233.1385	$233.14	$233.15	$233.10
Purchase #2	$6.83	12.375%	$7.6752	$7.68	$7.70	$7.70
Purchase #3	$207.73	9.334%	$227.1195	$227.12	$227.10	$227.10
Purchase #4	$61.71	8.592%	$67.0121	$67.01	$67.00	$67.00
Purchase #5	$40.97	10.660%	$45.3374	$45.34	$45.35	$45.30
Purchase #6	$74.86	5.347%	$78.8628	$78.86	$78.85	$78.90
Purchase #7	$177.38	3.487%	$183.5652	$183.57	$183.55	$183.60
7 purchase totals =	$792.37		$842.7107	$842.72	$842.70	$842.70