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	$217.44	12.618%	$244.8766	$244.88	$244.90	$244.90
Purchase #2	$121.98	12.864%	$137.6715	$137.67	$137.65	$137.70
Purchase #3	$173.71	13.210%	$196.6571	$196.66	$196.65	$196.70
Purchase #4	$188.73	4.296%	$196.8378	$196.84	$196.85	$196.80
Purchase #5	$212.56	12.647%	$239.4425	$239.44	$239.45	$239.40
Purchase #6	$98.35	7.369%	$105.5974	$105.60	$105.60	$105.60
Purchase #7	$241.91	5.375%	$254.9127	$254.91	$254.90	$254.90
7 purchase totals =	$1,254.68		$1,375.9956	$1,376.00	$1,376.00	$1,376.00