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	$49.84	3.553%	$51.6108	$51.61	$51.60	$51.60
Purchase #2	$229.86	5.171%	$241.7461	$241.75	$241.75	$241.70
Purchase #3	$72.86	10.804%	$80.7318	$80.73	$80.75	$80.70
Purchase #4	$102.79	11.429%	$114.5379	$114.54	$114.55	$114.50
Purchase #5	$217.63	7.458%	$233.8608	$233.86	$233.85	$233.90
Purchase #6	$34.80	8.864%	$37.8847	$37.88	$37.90	$37.90
Purchase #7	$223.35	8.220%	$241.7094	$241.71	$241.70	$241.70
7 purchase totals =	$931.13		$1,002.0815	$1,002.08	$1,002.10	$1,002.00