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	$78.75	13.822%	$89.6348	$89.63	$89.65	$89.60
Purchase #2	$36.87	11.126%	$40.9722	$40.97	$40.95	$41.00
Purchase #3	$61.89	12.442%	$69.5904	$69.59	$69.60	$69.60
Purchase #4	$153.67	13.214%	$173.976	$173.98	$174.00	$174.00
Purchase #5	$75.98	8.397%	$82.36	$82.36	$82.35	$82.40
Purchase #6	$180.46	5.661%	$190.6758	$190.68	$190.70	$190.70
Purchase #7	$42.60	4.472%	$44.5051	$44.51	$44.50	$44.50
7 purchase totals =	$630.22		$691.7143	$691.72	$691.75	$691.80