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	$62.32	12.493%	$70.1056	$70.11	$70.10	$70.10
Purchase #2	$186.68	7.334%	$200.3711	$200.37	$200.35	$200.40
Purchase #3	$40.43	5.208%	$42.5356	$42.54	$42.55	$42.50
Purchase #4	$54.81	3.150%	$56.5365	$56.54	$56.55	$56.50
Purchase #5	$156.66	5.409%	$165.1337	$165.13	$165.15	$165.10
Purchase #6	$62.76	5.131%	$65.9802	$65.98	$66.00	$66.00
Purchase #7	$172.82	10.314%	$190.6447	$190.64	$190.65	$190.60
7 purchase totals =	$736.48		$791.3074	$791.31	$791.35	$791.20