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	$227.27	10.607%	$251.3765	$251.38	$251.40	$251.40
Purchase #2	$132.58	13.810%	$150.8893	$150.89	$150.90	$150.90
Purchase #3	$34.99	5.709%	$36.9876	$36.99	$37.00	$37.00
Purchase #4	$246.81	3.799%	$256.1863	$256.19	$256.20	$256.20
Purchase #5	$233.87	6.514%	$249.1043	$249.10	$249.10	$249.10
Purchase #6	$14.80	11.369%	$16.4826	$16.48	$16.50	$16.50
Purchase #7	$136.40	10.435%	$150.6333	$150.63	$150.65	$150.60
7 purchase totals =	$1,026.72		$1,111.6599	$1,111.66	$1,111.75	$1,111.70