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	$138.37	7.557%	$148.8266	$148.83	$148.85	$148.80
Purchase #2	$188.96	12.452%	$212.4893	$212.49	$212.50	$212.50
Purchase #3	$212.25	12.512%	$238.8067	$238.81	$238.80	$238.80
Purchase #4	$59.42	11.646%	$66.3401	$66.34	$66.35	$66.30
Purchase #5	$103.70	4.783%	$108.66	$108.66	$108.65	$108.70
Purchase #6	$156.34	11.254%	$173.9345	$173.93	$173.95	$173.90
Purchase #7	$116.94	12.425%	$131.4698	$131.47	$131.45	$131.50
7 purchase totals =	$975.98		$1,080.5270	$1,080.53	$1,080.55	$1,080.50