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	$185.69	5.513%	$195.9271	$195.93	$195.95	$195.90
Purchase #2	$90.26	10.537%	$99.7707	$99.77	$99.75	$99.80
Purchase #3	$246.47	4.428%	$257.3837	$257.38	$257.40	$257.40
Purchase #4	$45.42	4.410%	$47.423	$47.42	$47.40	$47.40
Purchase #5	$39.37	10.287%	$43.42	$43.42	$43.40	$43.40
Purchase #6	$80.90	11.503%	$90.2059	$90.21	$90.20	$90.20
Purchase #7	$159.83	9.429%	$174.9004	$174.90	$174.90	$174.90
7 purchase totals =	$847.94		$909.0308	$909.03	$909.00	$909.00