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	$208.89	4.245%	$217.7574	$217.76	$217.75	$217.80
Purchase #2	$57.67	6.654%	$61.5074	$61.51	$61.50	$61.50
Purchase #3	$111.48	7.154%	$119.4553	$119.46	$119.45	$119.50
Purchase #4	$145.63	7.356%	$156.3425	$156.34	$156.35	$156.30
Purchase #5	$61.82	3.278%	$63.8465	$63.85	$63.85	$63.80
Purchase #6	$61.57	12.804%	$69.4534	$69.45	$69.45	$69.50
Purchase #7	$151.25	12.458%	$170.0927	$170.09	$170.10	$170.10
7 purchase totals =	$798.31		$858.4552	$858.46	$858.45	$858.50