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	$87.69	3.457%	$90.7214	$90.72	$90.70	$90.70
Purchase #2	$35.98	10.711%	$39.8338	$39.83	$39.85	$39.80
Purchase #3	$57.30	3.102%	$59.0774	$59.08	$59.10	$59.10
Purchase #4	$186.68	8.341%	$202.251	$202.25	$202.25	$202.30
Purchase #5	$81.76	13.488%	$92.7878	$92.79	$92.80	$92.80
Purchase #6	$47.38	9.148%	$51.7143	$51.71	$51.70	$51.70
Purchase #7	$104.90	13.223%	$118.7709	$118.77	$118.75	$118.80
7 purchase totals =	$601.69		$655.1566	$655.15	$655.15	$655.20