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	$201.89	13.468%	$229.0805	$229.08	$229.10	$229.10
Purchase #2	$184.86	8.442%	$200.4659	$200.47	$200.45	$200.50
Purchase #3	$151.65	10.363%	$167.3655	$167.37	$167.35	$167.40
Purchase #4	$54.97	11.604%	$61.3487	$61.35	$61.35	$61.30
Purchase #5	$150.34	6.483%	$160.0865	$160.09	$160.10	$160.10
Purchase #6	$87.33	8.754%	$94.9749	$94.97	$94.95	$95.00
Purchase #7	$87.92	12.808%	$99.1808	$99.18	$99.20	$99.20
7 purchase totals =	$918.96		$1,012.5028	$1,012.51	$1,012.50	$1,012.60