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	$93.54	10.657%	$103.5086	$103.51	$103.50	$103.50
Purchase #2	$46.78	4.560%	$48.9132	$48.91	$48.90	$48.90
Purchase #3	$124.82	7.295%	$133.9256	$133.93	$133.95	$133.90
Purchase #4	$234.89	3.459%	$243.0148	$243.01	$243.00	$243.00
Purchase #5	$116.90	12.705%	$131.7521	$131.75	$131.75	$131.80
Purchase #6	$221.68	4.559%	$231.7864	$231.79	$231.80	$231.80
Purchase #7	$106.98	13.635%	$121.5667	$121.57	$121.55	$121.60
7 purchase totals =	$945.59		$1,014.4674	$1,014.47	$1,014.45	$1,014.50