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	$236.56	9.844%	$259.847	$259.85	$259.85	$259.80
Purchase #2	$227.40	11.582%	$253.7375	$253.74	$253.75	$253.70
Purchase #3	$131.54	8.257%	$142.4013	$142.40	$142.40	$142.40
Purchase #4	$230.69	7.739%	$248.5431	$248.54	$248.55	$248.50
Purchase #5	$34.47	9.591%	$37.776	$37.78	$37.80	$37.80
Purchase #6	$70.85	4.288%	$73.888	$73.89	$73.90	$73.90
Purchase #7	$219.27	6.301%	$233.0862	$233.09	$233.10	$233.10
7 purchase totals =	$1,150.78		$1,249.2791	$1,249.29	$1,249.35	$1,249.20