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	$141.59	4.448%	$147.8879	$147.89	$147.90	$147.90
Purchase #2	$113.89	9.215%	$124.385	$124.39	$124.40	$124.40
Purchase #3	$123.41	11.553%	$137.6676	$137.67	$137.65	$137.70
Purchase #4	$249.40	12.141%	$279.6797	$279.68	$279.70	$279.70
Purchase #5	$60.73	5.676%	$64.177	$64.18	$64.20	$64.20
Purchase #6	$102.82	13.173%	$116.3645	$116.36	$116.35	$116.40
Purchase #7	$131.66	7.340%	$141.3238	$141.32	$141.30	$141.30
7 purchase totals =	$923.50		$1,011.4855	$1,011.49	$1,011.50	$1,011.60