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	$63.44	3.487%	$65.6522	$65.65	$65.65	$65.70
Purchase #2	$124.82	11.646%	$139.3565	$139.36	$139.35	$139.40
Purchase #3	$203.97	13.383%	$231.2673	$231.27	$231.25	$231.30
Purchase #4	$73.97	11.667%	$82.6001	$82.60	$82.60	$82.60
Purchase #5	$214.90	3.689%	$222.8277	$222.83	$222.85	$222.80
Purchase #6	$10.67	8.119%	$11.5363	$11.54	$11.55	$11.50
Purchase #7	$63.71	12.218%	$71.4941	$71.49	$71.50	$71.50
7 purchase totals =	$755.48		$824.7342	$824.74	$824.75	$824.80