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	$203.98	5.844%	$215.9006	$215.90	$215.90	$215.90
Purchase #2	$101.88	3.618%	$105.566	$105.57	$105.55	$105.60
Purchase #3	$138.63	10.162%	$152.7176	$152.72	$152.70	$152.70
Purchase #4	$41.48	13.342%	$47.0143	$47.01	$47.00	$47.00
Purchase #5	$138.93	9.779%	$152.516	$152.52	$152.50	$152.50
Purchase #6	$85.36	6.547%	$90.9485	$90.95	$90.95	$90.90
Purchase #7	$27.98	3.540%	$28.9705	$28.97	$28.95	$29.00
7 purchase totals =	$738.24		$793.6335	$793.64	$793.55	$793.60