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	$84.45	4.200%	$87.9969	$88.00	$88.00	$88.00
Purchase #2	$39.58	3.585%	$40.9989	$41.00	$41.00	$41.00
Purchase #3	$66.93	8.119%	$72.364	$72.36	$72.35	$72.40
Purchase #4	$62.55	8.149%	$67.6472	$67.65	$67.65	$67.60
Purchase #5	$117.85	13.761%	$134.0673	$134.07	$134.05	$134.10
Purchase #6	$18.76	8.421%	$20.3398	$20.34	$20.35	$20.30
Purchase #7	$33.49	12.238%	$37.5885	$37.59	$37.60	$37.60
7 purchase totals =	$423.61		$461.0026	$461.01	$461.00	$461.00