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	$113.41	7.837%	$122.2979	$122.30	$122.30	$122.30
Purchase #2	$95.59	8.261%	$103.4867	$103.49	$103.50	$103.50
Purchase #3	$211.52	12.566%	$238.0996	$238.10	$238.10	$238.10
Purchase #4	$31.88	5.347%	$33.5846	$33.58	$33.60	$33.60
Purchase #5	$136.79	11.753%	$152.8669	$152.87	$152.85	$152.90
Purchase #6	$139.60	12.327%	$156.8085	$156.81	$156.80	$156.80
Purchase #7	$214.81	9.306%	$234.8002	$234.80	$234.80	$234.80
7 purchase totals =	$943.60		$1,041.9444	$1,041.95	$1,041.95	$1,042.00