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	$221.44	5.453%	$233.5151	$233.52	$233.50	$233.50
Purchase #2	$187.78	13.715%	$213.534	$213.53	$213.55	$213.50
Purchase #3	$47.73	10.767%	$52.8691	$52.87	$52.85	$52.90
Purchase #4	$6.49	6.657%	$6.922	$6.92	$6.90	$6.90
Purchase #5	$57.46	10.441%	$63.4594	$63.46	$63.45	$63.50
Purchase #6	$35.54	9.457%	$38.901	$38.90	$38.90	$38.90
Purchase #7	$46.33	11.862%	$51.8257	$51.83	$51.85	$51.80
7 purchase totals =	$602.77		$661.0263	$661.03	$661.00	$661.00