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	$66.33	8.741%	$72.1279	$72.13	$72.15	$72.10
Purchase #2	$220.27	8.270%	$238.4863	$238.49	$238.50	$238.50
Purchase #3	$139.46	8.133%	$150.8023	$150.80	$150.80	$150.80
Purchase #4	$24.31	13.773%	$27.6582	$27.66	$27.65	$27.70
Purchase #5	$87.30	3.580%	$90.4253	$90.43	$90.45	$90.40
Purchase #6	$187.25	4.832%	$196.2979	$196.30	$196.30	$196.30
Purchase #7	$29.50	6.519%	$31.4231	$31.42	$31.40	$31.40
7 purchase totals =	$754.42		$807.2210	$807.23	$807.25	$807.20