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	$112.51	5.637%	$118.8522	$118.85	$118.85	$118.90
Purchase #2	$69.54	3.423%	$71.9204	$71.92	$71.90	$71.90
Purchase #3	$56.75	5.601%	$59.9286	$59.93	$59.95	$59.90
Purchase #4	$168.41	5.604%	$177.8477	$177.85	$177.85	$177.80
Purchase #5	$242.96	5.357%	$255.9754	$255.98	$256.00	$256.00
Purchase #6	$120.95	8.113%	$130.7627	$130.76	$130.75	$130.80
Purchase #7	$118.77	10.124%	$130.7943	$130.79	$130.80	$130.80
7 purchase totals =	$889.89		$946.0813	$946.08	$946.10	$946.10