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	$98.72	11.254%	$109.8299	$109.83	$109.85	$109.80
Purchase #2	$169.85	4.824%	$178.0436	$178.04	$178.05	$178.00
Purchase #3	$238.32	7.154%	$255.3694	$255.37	$255.35	$255.40
Purchase #4	$192.79	10.264%	$212.578	$212.58	$212.60	$212.60
Purchase #5	$226.86	5.121%	$238.4775	$238.48	$238.50	$238.50
Purchase #6	$221.92	8.402%	$240.5657	$240.57	$240.55	$240.60
Purchase #7	$42.34	10.132%	$46.6299	$46.63	$46.65	$46.60
7 purchase totals =	$1,190.80		$1,281.4940	$1,281.50	$1,281.55	$1,281.50