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	$212.28	13.562%	$241.0694	$241.07	$241.05	$241.10
Purchase #2	$58.61	11.830%	$65.5436	$65.54	$65.55	$65.50
Purchase #3	$67.71	4.257%	$70.5924	$70.59	$70.60	$70.60
Purchase #4	$248.60	12.694%	$280.1573	$280.16	$280.15	$280.20
Purchase #5	$187.51	4.809%	$196.5274	$196.53	$196.55	$196.50
Purchase #6	$126.80	12.387%	$142.5067	$142.51	$142.50	$142.50
Purchase #7	$87.38	7.674%	$94.0855	$94.09	$94.10	$94.10
7 purchase totals =	$988.89		$1,090.4823	$1,090.49	$1,090.50	$1,090.50