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	$232.82	11.508%	$259.6129	$259.61	$259.60	$259.60
Purchase #2	$10.46	5.445%	$11.0295	$11.03	$11.05	$11.00
Purchase #3	$42.63	5.806%	$45.1051	$45.11	$45.10	$45.10
Purchase #4	$32.58	10.203%	$35.9041	$35.90	$35.90	$35.90
Purchase #5	$83.70	10.559%	$92.5379	$92.54	$92.55	$92.50
Purchase #6	$214.34	4.665%	$224.339	$224.34	$224.35	$224.30
Purchase #7	$208.36	9.710%	$228.5918	$228.59	$228.60	$228.60
7 purchase totals =	$824.89		$897.1203	$897.12	$897.15	$897.00