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	$239.95	9.585%	$262.9492	$262.95	$262.95	$262.90
Purchase #2	$74.51	12.603%	$83.9005	$83.90	$83.90	$83.90
Purchase #3	$242.90	6.751%	$259.2982	$259.30	$259.30	$259.30
Purchase #4	$228.39	9.169%	$249.3311	$249.33	$249.35	$249.30
Purchase #5	$16.26	11.574%	$18.1419	$18.14	$18.15	$18.10
Purchase #6	$182.83	7.629%	$196.7781	$196.78	$196.80	$196.80
Purchase #7	$86.54	5.236%	$91.0712	$91.07	$91.05	$91.10
7 purchase totals =	$1,071.38		$1,161.4702	$1,161.47	$1,161.50	$1,161.40