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	$95.33	7.480%	$102.4607	$102.46	$102.45	$102.50
Purchase #2	$140.52	11.716%	$156.9833	$156.98	$157.00	$157.00
Purchase #3	$82.37	4.771%	$86.2999	$86.30	$86.30	$86.30
Purchase #4	$244.28	10.310%	$269.4653	$269.47	$269.45	$269.50
Purchase #5	$211.72	8.518%	$229.7543	$229.75	$229.75	$229.80
Purchase #6	$31.78	9.651%	$34.8471	$34.85	$34.85	$34.80
Purchase #7	$127.79	3.151%	$131.8167	$131.82	$131.80	$131.80
7 purchase totals =	$933.79		$1,011.6273	$1,011.63	$1,011.60	$1,011.70