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	$233.44	12.345%	$262.2582	$262.26	$262.25	$262.30
Purchase #2	$163.73	10.754%	$181.3375	$181.34	$181.35	$181.30
Purchase #3	$139.62	10.518%	$154.3052	$154.31	$154.30	$154.30
Purchase #4	$29.52	5.680%	$31.1967	$31.20	$31.20	$31.20
Purchase #5	$199.54	13.131%	$225.7416	$225.74	$225.75	$225.70
Purchase #6	$158.47	6.419%	$168.6422	$168.64	$168.65	$168.60
Purchase #7	$39.42	7.290%	$42.2937	$42.29	$42.30	$42.30
7 purchase totals =	$963.74		$1,065.7751	$1,065.78	$1,065.80	$1,065.70