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	$249.33	13.480%	$282.9397	$282.94	$282.95	$282.90
Purchase #2	$41.25	11.228%	$45.8816	$45.88	$45.90	$45.90
Purchase #3	$235.30	11.477%	$262.3054	$262.31	$262.30	$262.30
Purchase #4	$141.59	5.185%	$148.9314	$148.93	$148.95	$148.90
Purchase #5	$185.27	12.394%	$208.2324	$208.23	$208.25	$208.20
Purchase #6	$9.92	11.240%	$11.035	$11.04	$11.05	$11.00
Purchase #7	$198.75	9.395%	$217.4226	$217.42	$217.40	$217.40
7 purchase totals =	$1,061.41		$1,176.7481	$1,176.75	$1,176.80	$1,176.60