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	$86.25	4.209%	$89.8803	$89.88	$89.90	$89.90
Purchase #2	$136.81	3.458%	$141.5409	$141.54	$141.55	$141.50
Purchase #3	$132.38	6.797%	$141.3779	$141.38	$141.40	$141.40
Purchase #4	$186.57	7.146%	$199.9023	$199.90	$199.90	$199.90
Purchase #5	$137.72	11.323%	$153.314	$153.31	$153.30	$153.30
Purchase #6	$147.39	4.469%	$153.9769	$153.98	$154.00	$154.00
Purchase #7	$250.32	9.308%	$273.6198	$273.62	$273.60	$273.60
7 purchase totals =	$1,077.44		$1,153.6121	$1,153.61	$1,153.65	$1,153.60