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	$90.61	5.873%	$95.9315	$95.93	$95.95	$95.90
Purchase #2	$37.78	9.536%	$41.3827	$41.38	$41.40	$41.40
Purchase #3	$239.86	7.692%	$258.31	$258.31	$258.30	$258.30
Purchase #4	$164.68	6.352%	$175.1405	$175.14	$175.15	$175.10
Purchase #5	$50.53	6.694%	$53.9125	$53.91	$53.90	$53.90
Purchase #6	$120.81	10.839%	$133.9046	$133.90	$133.90	$133.90
Purchase #7	$86.66	12.801%	$97.7533	$97.75	$97.75	$97.80
7 purchase totals =	$790.93		$856.3351	$856.32	$856.35	$856.30