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	$112.82	9.312%	$123.3258	$123.33	$123.35	$123.30
Purchase #2	$232.54	4.450%	$242.888	$242.89	$242.90	$242.90
Purchase #3	$129.82	9.668%	$142.371	$142.37	$142.35	$142.40
Purchase #4	$136.83	4.620%	$143.1515	$143.15	$143.15	$143.20
Purchase #5	$86.97	11.702%	$97.1472	$97.15	$97.15	$97.10
Purchase #6	$51.42	9.751%	$56.434	$56.43	$56.45	$56.40
Purchase #7	$49.60	7.826%	$53.4817	$53.48	$53.50	$53.50
7 purchase totals =	$800.00		$858.7992	$858.80	$858.85	$858.80