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	$52.31	6.590%	$55.7572	$55.76	$55.75	$55.80
Purchase #2	$89.93	3.258%	$92.8599	$92.86	$92.85	$92.90
Purchase #3	$45.78	9.768%	$50.2518	$50.25	$50.25	$50.30
Purchase #4	$89.99	8.163%	$97.3359	$97.34	$97.35	$97.30
Purchase #5	$10.98	8.518%	$11.9153	$11.92	$11.90	$11.90
Purchase #6	$212.78	5.195%	$223.8339	$223.83	$223.85	$223.80
Purchase #7	$202.69	7.304%	$217.4945	$217.49	$217.50	$217.50
7 purchase totals =	$704.46		$749.4485	$749.45	$749.45	$749.50