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	$143.81	4.404%	$150.1434	$150.14	$150.15	$150.10
Purchase #2	$150.90	11.284%	$167.9276	$167.93	$167.95	$167.90
Purchase #3	$177.84	11.576%	$198.4268	$198.43	$198.45	$198.40
Purchase #4	$218.59	11.347%	$243.3934	$243.39	$243.40	$243.40
Purchase #5	$84.93	5.426%	$89.5383	$89.54	$89.55	$89.50
Purchase #6	$207.36	9.808%	$227.6979	$227.70	$227.70	$227.70
Purchase #7	$20.46	4.588%	$21.3987	$21.40	$21.40	$21.40
7 purchase totals =	$1,003.89		$1,098.5261	$1,098.53	$1,098.60	$1,098.40