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	$42.28	8.847%	$46.0205	$46.02	$46.00	$46.00
Purchase #2	$152.28	10.249%	$167.8872	$167.89	$167.90	$167.90
Purchase #3	$239.62	8.219%	$259.3144	$259.31	$259.30	$259.30
Purchase #4	$96.98	5.596%	$102.407	$102.41	$102.40	$102.40
Purchase #5	$83.66	3.404%	$86.5078	$86.51	$86.50	$86.50
Purchase #6	$36.39	6.758%	$38.8492	$38.85	$38.85	$38.80
Purchase #7	$240.31	6.798%	$256.6463	$256.65	$256.65	$256.60
7 purchase totals =	$891.52		$957.6324	$957.64	$957.60	$957.50