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	$198.52	13.233%	$224.7902	$224.79	$224.80	$224.80
Purchase #2	$114.36	12.414%	$128.5567	$128.56	$128.55	$128.60
Purchase #3	$242.48	11.605%	$270.6198	$270.62	$270.60	$270.60
Purchase #4	$119.46	3.468%	$123.6029	$123.60	$123.60	$123.60
Purchase #5	$162.34	3.821%	$168.543	$168.54	$168.55	$168.50
Purchase #6	$222.45	7.219%	$238.5087	$238.51	$238.50	$238.50
Purchase #7	$226.71	12.392%	$254.8039	$254.80	$254.80	$254.80
7 purchase totals =	$1,286.32		$1,409.4252	$1,409.42	$1,409.40	$1,409.40