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	$67.76	7.544%	$72.8718	$72.87	$72.85	$72.90
Purchase #2	$54.56	10.453%	$60.2632	$60.26	$60.25	$60.30
Purchase #3	$130.53	8.714%	$141.9044	$141.90	$141.90	$141.90
Purchase #4	$167.27	4.291%	$174.4476	$174.45	$174.45	$174.40
Purchase #5	$179.97	13.634%	$204.5071	$204.51	$204.50	$204.50
Purchase #6	$31.82	3.522%	$32.9407	$32.94	$32.95	$32.90
Purchase #7	$42.70	5.107%	$44.8807	$44.88	$44.90	$44.90
7 purchase totals =	$674.61		$731.8155	$731.81	$731.80	$731.80