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	$11.49	9.463%	$12.5773	$12.58	$12.60	$12.60
Purchase #2	$197.97	12.155%	$222.0333	$222.03	$222.05	$222.00
Purchase #3	$172.64	4.805%	$180.9354	$180.94	$180.95	$180.90
Purchase #4	$81.69	4.216%	$85.1341	$85.13	$85.15	$85.10
Purchase #5	$192.73	3.395%	$199.2732	$199.27	$199.25	$199.30
Purchase #6	$181.87	4.760%	$190.527	$190.53	$190.55	$190.50
Purchase #7	$243.76	13.477%	$276.6115	$276.61	$276.60	$276.60
7 purchase totals =	$1,082.15		$1,167.0918	$1,167.09	$1,167.15	$1,167.00