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	$126.63	9.414%	$138.5509	$138.55	$138.55	$138.60
Purchase #2	$233.40	10.743%	$258.4742	$258.47	$258.45	$258.50
Purchase #3	$73.77	11.403%	$82.182	$82.18	$82.20	$82.20
Purchase #4	$175.86	13.482%	$199.5694	$199.57	$199.55	$199.60
Purchase #5	$138.51	3.817%	$143.7969	$143.80	$143.80	$143.80
Purchase #6	$133.84	4.261%	$139.5429	$139.54	$139.55	$139.50
Purchase #7	$103.38	7.575%	$111.211	$111.21	$111.20	$111.20
7 purchase totals =	$985.39		$1,073.3273	$1,073.32	$1,073.30	$1,073.40