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	$221.92	6.354%	$236.0208	$236.02	$236.00	$236.00
Purchase #2	$54.89	7.585%	$59.0534	$59.05	$59.05	$59.10
Purchase #3	$177.97	12.165%	$199.6201	$199.62	$199.60	$199.60
Purchase #4	$114.92	11.234%	$127.8301	$127.83	$127.85	$127.80
Purchase #5	$80.60	7.284%	$86.4709	$86.47	$86.45	$86.50
Purchase #6	$87.79	6.281%	$93.3041	$93.30	$93.30	$93.30
Purchase #7	$233.76	9.504%	$255.9766	$255.98	$256.00	$256.00
7 purchase totals =	$971.85		$1,058.2760	$1,058.27	$1,058.25	$1,058.30