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	$218.72	6.744%	$233.4705	$233.47	$233.45	$233.50
Purchase #2	$167.83	11.572%	$187.2513	$187.25	$187.25	$187.30
Purchase #3	$170.33	11.152%	$189.3252	$189.33	$189.35	$189.30
Purchase #4	$97.73	4.754%	$102.3761	$102.38	$102.40	$102.40
Purchase #5	$30.61	12.106%	$34.3156	$34.32	$34.30	$34.30
Purchase #6	$208.29	5.685%	$220.1313	$220.13	$220.15	$220.10
Purchase #7	$46.39	6.650%	$49.4749	$49.47	$49.45	$49.50
7 purchase totals =	$939.90		$1,016.3449	$1,016.35	$1,016.35	$1,016.40