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	$198.73	13.119%	$224.8014	$224.80	$224.80	$224.80
Purchase #2	$63.45	3.787%	$65.8529	$65.85	$65.85	$65.90
Purchase #3	$99.43	4.403%	$103.8079	$103.81	$103.80	$103.80
Purchase #4	$115.41	5.218%	$121.4321	$121.43	$121.45	$121.40
Purchase #5	$118.47	10.851%	$131.3252	$131.33	$131.35	$131.30
Purchase #6	$122.67	7.558%	$131.9414	$131.94	$131.95	$131.90
Purchase #7	$206.84	7.588%	$222.535	$222.54	$222.55	$222.50
7 purchase totals =	$925.00		$1,001.6959	$1,001.70	$1,001.75	$1,001.60