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	$131.39	7.240%	$140.9026	$140.90	$140.90	$140.90
Purchase #2	$48.67	4.474%	$50.8475	$50.85	$50.85	$50.80
Purchase #3	$230.76	13.442%	$261.7788	$261.78	$261.80	$261.80
Purchase #4	$116.29	9.376%	$127.1934	$127.19	$127.20	$127.20
Purchase #5	$162.58	12.107%	$182.2636	$182.26	$182.25	$182.30
Purchase #6	$129.53	12.366%	$145.5477	$145.55	$145.55	$145.50
Purchase #7	$144.92	10.757%	$160.509	$160.51	$160.50	$160.50
7 purchase totals =	$964.14		$1,069.0426	$1,069.04	$1,069.05	$1,069.00