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	$130.92	7.621%	$140.8974	$140.90	$140.90	$140.90
Purchase #2	$151.53	9.409%	$165.7875	$165.79	$165.80	$165.80
Purchase #3	$96.36	13.327%	$109.2019	$109.20	$109.20	$109.20
Purchase #4	$85.96	3.794%	$89.2213	$89.22	$89.20	$89.20
Purchase #5	$166.51	5.304%	$175.3417	$175.34	$175.35	$175.30
Purchase #6	$163.99	12.706%	$184.8266	$184.83	$184.85	$184.80
Purchase #7	$78.80	4.605%	$82.4287	$82.43	$82.45	$82.40
7 purchase totals =	$874.07		$947.7051	$947.71	$947.75	$947.60