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	$140.46	9.437%	$153.7152	$153.72	$153.70	$153.70
Purchase #2	$178.80	5.759%	$189.0971	$189.10	$189.10	$189.10
Purchase #3	$72.49	8.722%	$78.8126	$78.81	$78.80	$78.80
Purchase #4	$115.86	6.682%	$123.6018	$123.60	$123.60	$123.60
Purchase #5	$146.42	9.199%	$159.8892	$159.89	$159.90	$159.90
Purchase #6	$177.85	12.197%	$199.5424	$199.54	$199.55	$199.50
Purchase #7	$204.65	11.646%	$228.4835	$228.48	$228.50	$228.50
7 purchase totals =	$1,036.53		$1,133.1418	$1,133.14	$1,133.15	$1,133.10