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	$191.83	8.357%	$207.8612	$207.86	$207.85	$207.90
Purchase #2	$160.34	4.449%	$167.4735	$167.47	$167.45	$167.50
Purchase #3	$38.75	4.450%	$40.4744	$40.47	$40.45	$40.50
Purchase #4	$204.32	8.631%	$221.9549	$221.95	$221.95	$222.00
Purchase #5	$82.33	11.844%	$92.0812	$92.08	$92.10	$92.10
Purchase #6	$120.62	3.575%	$124.9322	$124.93	$124.95	$124.90
Purchase #7	$80.38	10.816%	$89.0739	$89.07	$89.05	$89.10
7 purchase totals =	$878.57		$943.8513	$943.83	$943.80	$944.00