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	$218.34	4.348%	$227.8334	$227.83	$227.85	$227.80
Purchase #2	$98.88	5.494%	$104.3125	$104.31	$104.30	$104.30
Purchase #3	$39.31	3.176%	$40.5585	$40.56	$40.55	$40.60
Purchase #4	$29.76	13.723%	$33.844	$33.84	$33.85	$33.80
Purchase #5	$77.54	12.830%	$87.4884	$87.49	$87.50	$87.50
Purchase #6	$221.56	7.487%	$238.1482	$238.15	$238.15	$238.10
Purchase #7	$222.86	10.471%	$246.1957	$246.20	$246.20	$246.20
7 purchase totals =	$908.25		$978.3807	$978.38	$978.40	$978.30