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	$38.61	8.611%	$41.9347	$41.93	$41.95	$41.90
Purchase #2	$168.34	6.667%	$179.5632	$179.56	$179.55	$179.60
Purchase #3	$246.74	10.798%	$273.383	$273.38	$273.40	$273.40
Purchase #4	$122.98	3.638%	$127.454	$127.45	$127.45	$127.50
Purchase #5	$211.27	12.740%	$238.1858	$238.19	$238.20	$238.20
Purchase #6	$131.74	4.602%	$137.8027	$137.80	$137.80	$137.80
Purchase #7	$159.92	5.466%	$168.6612	$168.66	$168.65	$168.70
7 purchase totals =	$1,079.60		$1,166.9846	$1,166.97	$1,167.00	$1,167.10