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	$150.70	12.586%	$169.6671	$169.67	$169.65	$169.70
Purchase #2	$149.93	11.480%	$167.142	$167.14	$167.15	$167.10
Purchase #3	$69.59	5.644%	$73.5177	$73.52	$73.50	$73.50
Purchase #4	$102.57	8.397%	$111.1828	$111.18	$111.20	$111.20
Purchase #5	$199.35	13.571%	$226.4038	$226.40	$226.40	$226.40
Purchase #6	$178.96	3.153%	$184.6026	$184.60	$184.60	$184.60
Purchase #7	$92.59	7.220%	$99.275	$99.28	$99.30	$99.30
7 purchase totals =	$943.69		$1,031.7910	$1,031.79	$1,031.80	$1,031.80