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	$43.99	4.185%	$45.831	$45.83	$45.85	$45.80
Purchase #2	$33.88	9.173%	$36.9878	$36.99	$37.00	$37.00
Purchase #3	$158.95	6.187%	$168.7842	$168.78	$168.80	$168.80
Purchase #4	$20.78	5.429%	$21.9081	$21.91	$21.90	$21.90
Purchase #5	$32.73	12.630%	$36.8638	$36.86	$36.85	$36.90
Purchase #6	$97.86	11.646%	$109.2568	$109.26	$109.25	$109.30
Purchase #7	$219.83	12.323%	$246.9197	$246.92	$246.90	$246.90
7 purchase totals =	$608.02		$666.5514	$666.55	$666.55	$666.60