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	$83.38	3.302%	$86.1332	$86.13	$86.15	$86.10
Purchase #2	$57.77	7.569%	$62.1426	$62.14	$62.15	$62.10
Purchase #3	$189.90	8.663%	$206.351	$206.35	$206.35	$206.40
Purchase #4	$61.52	11.238%	$68.4336	$68.43	$68.45	$68.40
Purchase #5	$13.49	7.500%	$14.5018	$14.50	$14.50	$14.50
Purchase #6	$176.56	11.182%	$196.3029	$196.30	$196.30	$196.30
Purchase #7	$178.93	11.553%	$199.6018	$199.60	$199.60	$199.60
7 purchase totals =	$761.55		$833.4669	$833.45	$833.50	$833.40