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	$223.62	8.589%	$242.8267	$242.83	$242.85	$242.80
Purchase #2	$92.25	5.700%	$97.5083	$97.51	$97.50	$97.50
Purchase #3	$80.82	12.805%	$91.169	$91.17	$91.15	$91.20
Purchase #4	$100.53	11.387%	$111.9774	$111.98	$112.00	$112.00
Purchase #5	$234.74	12.784%	$264.7492	$264.75	$264.75	$264.70
Purchase #6	$111.40	5.175%	$117.165	$117.17	$117.15	$117.20
Purchase #7	$124.35	5.390%	$131.0525	$131.05	$131.05	$131.10
7 purchase totals =	$967.71		$1,056.4481	$1,056.46	$1,056.45	$1,056.50