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	$153.39	8.593%	$166.5708	$166.57	$166.55	$166.60
Purchase #2	$144.35	6.601%	$153.8785	$153.88	$153.90	$153.90
Purchase #3	$189.94	6.220%	$201.7543	$201.75	$201.75	$201.80
Purchase #4	$132.93	6.310%	$141.3179	$141.32	$141.30	$141.30
Purchase #5	$40.67	12.870%	$45.9042	$45.90	$45.90	$45.90
Purchase #6	$153.25	9.529%	$167.8532	$167.85	$167.85	$167.90
Purchase #7	$161.89	10.732%	$179.264	$179.26	$179.25	$179.30
7 purchase totals =	$976.42		$1,056.5429	$1,056.53	$1,056.50	$1,056.70