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	$49.78	8.223%	$53.8734	$53.87	$53.85	$53.90
Purchase #2	$138.34	8.168%	$149.6396	$149.64	$149.65	$149.60
Purchase #3	$123.97	5.650%	$130.9743	$130.97	$130.95	$131.00
Purchase #4	$62.35	4.267%	$65.0105	$65.01	$65.00	$65.00
Purchase #5	$63.36	3.780%	$65.755	$65.76	$65.75	$65.80
Purchase #6	$99.29	12.523%	$111.7241	$111.72	$111.70	$111.70
Purchase #7	$88.57	12.627%	$99.7537	$99.75	$99.75	$99.80
7 purchase totals =	$625.66		$676.7306	$676.72	$676.65	$676.80