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	$148.46	11.182%	$165.0608	$165.06	$165.05	$165.10
Purchase #2	$38.40	12.136%	$43.0602	$43.06	$43.05	$43.10
Purchase #3	$201.63	6.400%	$214.5343	$214.53	$214.55	$214.50
Purchase #4	$16.46	12.725%	$18.5545	$18.55	$18.55	$18.60
Purchase #5	$80.79	12.450%	$90.8484	$90.85	$90.85	$90.80
Purchase #6	$120.42	13.382%	$136.5346	$136.53	$136.55	$136.50
Purchase #7	$75.67	10.854%	$83.8832	$83.88	$83.90	$83.90
7 purchase totals =	$681.83		$752.4760	$752.46	$752.50	$752.50