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	$208.96	6.430%	$222.3961	$222.40	$222.40	$222.40
Purchase #2	$79.63	3.169%	$82.1535	$82.15	$82.15	$82.20
Purchase #3	$31.54	3.152%	$32.5341	$32.53	$32.55	$32.50
Purchase #4	$132.32	4.250%	$137.9436	$137.94	$137.95	$137.90
Purchase #5	$250.65	5.646%	$264.8017	$264.80	$264.80	$264.80
Purchase #6	$209.38	7.196%	$224.447	$224.45	$224.45	$224.40
Purchase #7	$32.76	12.502%	$36.8557	$36.86	$36.85	$36.90
7 purchase totals =	$945.24		$1,001.1317	$1,001.13	$1,001.15	$1,001.10