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	$236.87	9.199%	$258.6597	$258.66	$258.65	$258.70
Purchase #2	$56.41	5.600%	$59.569	$59.57	$59.55	$59.60
Purchase #3	$166.93	12.280%	$187.429	$187.43	$187.45	$187.40
Purchase #4	$55.97	13.438%	$63.4912	$63.49	$63.50	$63.50
Purchase #5	$68.37	6.651%	$72.9173	$72.92	$72.90	$72.90
Purchase #6	$196.68	4.590%	$205.7076	$205.71	$205.70	$205.70
Purchase #7	$83.54	3.423%	$86.3996	$86.40	$86.40	$86.40
7 purchase totals =	$864.77		$934.1734	$934.18	$934.15	$934.20