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	$247.93	5.766%	$262.2256	$262.23	$262.25	$262.20
Purchase #2	$204.74	12.541%	$230.4164	$230.42	$230.40	$230.40
Purchase #3	$188.63	5.425%	$198.8632	$198.86	$198.85	$198.90
Purchase #4	$136.83	13.118%	$154.7794	$154.78	$154.80	$154.80
Purchase #5	$114.59	12.480%	$128.8908	$128.89	$128.90	$128.90
Purchase #6	$31.48	4.565%	$32.9171	$32.92	$32.90	$32.90
Purchase #7	$29.68	5.443%	$31.2955	$31.30	$31.30	$31.30
7 purchase totals =	$953.88		$1,039.3880	$1,039.40	$1,039.40	$1,039.40