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	$96.51	13.189%	$109.2387	$109.24	$109.25	$109.20
Purchase #2	$188.56	6.268%	$200.3789	$200.38	$200.40	$200.40
Purchase #3	$236.93	12.240%	$265.9302	$265.93	$265.95	$265.90
Purchase #4	$109.54	4.401%	$114.3609	$114.36	$114.35	$114.40
Purchase #5	$206.79	9.366%	$226.158	$226.16	$226.15	$226.20
Purchase #6	$78.50	6.508%	$83.6088	$83.61	$83.60	$83.60
Purchase #7	$59.84	6.598%	$63.7882	$63.79	$63.80	$63.80
7 purchase totals =	$976.67		$1,063.4637	$1,063.47	$1,063.50	$1,063.50