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	$52.34	10.465%	$57.8174	$57.82	$57.80	$57.80
Purchase #2	$67.30	5.238%	$70.8252	$70.83	$70.85	$70.80
Purchase #3	$154.94	3.542%	$160.428	$160.43	$160.45	$160.40
Purchase #4	$140.91	8.349%	$152.6746	$152.67	$152.65	$152.70
Purchase #5	$216.58	10.265%	$238.8119	$238.81	$238.80	$238.80
Purchase #6	$249.96	3.231%	$258.0362	$258.04	$258.05	$258.00
Purchase #7	$88.63	3.815%	$92.0112	$92.01	$92.00	$92.00
7 purchase totals =	$970.66		$1,030.6045	$1,030.61	$1,030.60	$1,030.50