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	$163.32	5.301%	$171.9776	$171.98	$172.00	$172.00
Purchase #2	$124.79	5.446%	$131.5861	$131.59	$131.60	$131.60
Purchase #3	$65.73	9.383%	$71.8974	$71.90	$71.90	$71.90
Purchase #4	$125.56	5.554%	$132.5336	$132.53	$132.55	$132.50
Purchase #5	$174.66	12.196%	$195.9615	$195.96	$195.95	$196.00
Purchase #6	$147.35	4.393%	$153.8231	$153.82	$153.80	$153.80
Purchase #7	$49.44	13.274%	$56.0027	$56.00	$56.00	$56.00
7 purchase totals =	$850.85		$913.7820	$913.78	$913.80	$913.80