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	$57.43	13.244%	$65.036	$65.04	$65.05	$65.00
Purchase #2	$161.42	6.405%	$171.759	$171.76	$171.75	$171.80
Purchase #3	$85.27	4.279%	$88.9187	$88.92	$88.90	$88.90
Purchase #4	$236.60	8.463%	$256.6235	$256.62	$256.60	$256.60
Purchase #5	$116.76	12.578%	$131.4461	$131.45	$131.45	$131.40
Purchase #6	$104.67	8.522%	$113.59	$113.59	$113.60	$113.60
Purchase #7	$119.96	9.357%	$131.1847	$131.18	$131.20	$131.20
7 purchase totals =	$882.11		$958.5580	$958.56	$958.55	$958.50