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	$103.62	5.717%	$109.544	$109.54	$109.55	$109.50
Purchase #2	$154.75	8.684%	$168.1885	$168.19	$168.20	$168.20
Purchase #3	$241.85	12.313%	$271.629	$271.63	$271.65	$271.60
Purchase #4	$94.73	12.392%	$106.4689	$106.47	$106.45	$106.50
Purchase #5	$99.60	11.534%	$111.0879	$111.09	$111.10	$111.10
Purchase #6	$133.99	8.855%	$145.8548	$145.85	$145.85	$145.90
Purchase #7	$137.30	7.235%	$147.2337	$147.23	$147.25	$147.20
7 purchase totals =	$965.84		$1,060.0068	$1,060.00	$1,060.05	$1,060.00