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	$158.70	8.104%	$171.561	$171.56	$171.55	$171.60
Purchase #2	$86.99	3.317%	$89.8755	$89.88	$89.90	$89.90
Purchase #3	$49.96	3.102%	$51.5098	$51.51	$51.50	$51.50
Purchase #4	$241.89	12.807%	$272.8689	$272.87	$272.85	$272.90
Purchase #5	$149.86	5.171%	$157.6093	$157.61	$157.60	$157.60
Purchase #6	$158.52	10.342%	$174.9141	$174.91	$174.90	$174.90
Purchase #7	$58.79	8.835%	$63.9841	$63.98	$64.00	$64.00
7 purchase totals =	$904.71		$982.3227	$982.32	$982.30	$982.40