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	$126.57	13.472%	$143.6215	$143.62	$143.60	$143.60
Purchase #2	$93.76	11.561%	$104.5996	$104.60	$104.60	$104.60
Purchase #3	$76.30	10.163%	$84.0544	$84.05	$84.05	$84.10
Purchase #4	$137.37	9.580%	$150.53	$150.53	$150.55	$150.50
Purchase #5	$108.51	6.796%	$115.8843	$115.88	$115.90	$115.90
Purchase #6	$246.71	3.848%	$256.2034	$256.20	$256.20	$256.20
Purchase #7	$233.33	5.216%	$245.5005	$245.50	$245.50	$245.50
7 purchase totals =	$1,022.55		$1,100.3937	$1,100.38	$1,100.40	$1,100.40