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	$148.88	10.160%	$164.0062	$164.01	$164.00	$164.00
Purchase #2	$57.42	11.382%	$63.9555	$63.96	$63.95	$64.00
Purchase #3	$35.83	13.447%	$40.6481	$40.65	$40.65	$40.60
Purchase #4	$74.85	13.535%	$84.9809	$84.98	$85.00	$85.00
Purchase #5	$64.72	12.614%	$72.8838	$72.88	$72.90	$72.90
Purchase #6	$141.71	13.449%	$160.7686	$160.77	$160.75	$160.80
Purchase #7	$184.96	9.278%	$202.1206	$202.12	$202.10	$202.10
7 purchase totals =	$708.37		$789.3637	$789.37	$789.35	$789.40