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	$209.57	7.189%	$224.636	$224.64	$224.65	$224.60
Purchase #2	$63.50	12.293%	$71.3061	$71.31	$71.30	$71.30
Purchase #3	$112.45	13.630%	$127.7769	$127.78	$127.80	$127.80
Purchase #4	$161.34	9.695%	$176.9819	$176.98	$177.00	$177.00
Purchase #5	$64.84	12.238%	$72.7751	$72.78	$72.80	$72.80
Purchase #6	$124.93	5.557%	$131.8724	$131.87	$131.85	$131.90
Purchase #7	$83.73	10.284%	$92.3408	$92.34	$92.35	$92.30
7 purchase totals =	$820.36		$897.6892	$897.70	$897.75	$897.70