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	$162.48	11.793%	$181.6413	$181.64	$181.65	$181.60
Purchase #2	$132.94	13.755%	$151.2259	$151.23	$151.25	$151.20
Purchase #3	$152.49	13.168%	$172.5699	$172.57	$172.55	$172.60
Purchase #4	$19.94	13.485%	$22.6289	$22.63	$22.65	$22.60
Purchase #5	$206.25	13.336%	$233.7555	$233.76	$233.75	$233.80
Purchase #6	$86.72	10.387%	$95.7276	$95.73	$95.75	$95.70
Purchase #7	$157.47	10.516%	$174.0295	$174.03	$174.05	$174.00
7 purchase totals =	$918.29		$1,031.5786	$1,031.59	$1,031.65	$1,031.50