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	$163.96	9.832%	$180.0805	$180.08	$180.10	$180.10
Purchase #2	$198.80	7.701%	$214.1096	$214.11	$214.10	$214.10
Purchase #3	$78.51	4.651%	$82.1615	$82.16	$82.15	$82.20
Purchase #4	$171.83	10.604%	$190.0509	$190.05	$190.05	$190.10
Purchase #5	$45.53	5.253%	$47.9217	$47.92	$47.90	$47.90
Purchase #6	$227.58	4.766%	$238.4265	$238.43	$238.45	$238.40
Purchase #7	$214.33	13.632%	$243.5475	$243.55	$243.55	$243.50
7 purchase totals =	$1,100.54		$1,196.2982	$1,196.30	$1,196.30	$1,196.30