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	$45.49	11.746%	$50.8333	$50.83	$50.85	$50.80
Purchase #2	$16.39	6.709%	$17.4896	$17.49	$17.50	$17.50
Purchase #3	$139.98	5.129%	$147.1596	$147.16	$147.15	$147.20
Purchase #4	$200.40	11.235%	$222.9149	$222.91	$222.90	$222.90
Purchase #5	$220.75	12.305%	$247.9133	$247.91	$247.90	$247.90
Purchase #6	$187.35	6.845%	$200.1741	$200.17	$200.15	$200.20
Purchase #7	$153.70	7.256%	$164.8525	$164.85	$164.85	$164.90
7 purchase totals =	$964.06		$1,051.3373	$1,051.32	$1,051.30	$1,051.40