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	$120.66	10.461%	$133.2822	$133.28	$133.30	$133.30
Purchase #2	$24.34	5.308%	$25.632	$25.63	$25.65	$25.60
Purchase #3	$233.79	7.552%	$251.4458	$251.45	$251.45	$251.40
Purchase #4	$106.40	11.395%	$118.5243	$118.52	$118.50	$118.50
Purchase #5	$16.78	12.758%	$18.9208	$18.92	$18.90	$18.90
Purchase #6	$145.66	4.423%	$152.1025	$152.10	$152.10	$152.10
Purchase #7	$67.65	6.576%	$72.0987	$72.10	$72.10	$72.10
7 purchase totals =	$715.28		$772.0063	$772.00	$772.00	$771.90