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	$108.40	9.804%	$119.0275	$119.03	$119.05	$119.00
Purchase #2	$150.96	5.206%	$158.819	$158.82	$158.80	$158.80
Purchase #3	$148.89	10.270%	$164.181	$164.18	$164.20	$164.20
Purchase #4	$195.49	10.299%	$215.6235	$215.62	$215.60	$215.60
Purchase #5	$213.45	4.705%	$223.4928	$223.49	$223.50	$223.50
Purchase #6	$112.75	13.175%	$127.6048	$127.60	$127.60	$127.60
Purchase #7	$37.52	7.330%	$40.2702	$40.27	$40.25	$40.30
7 purchase totals =	$967.46		$1,049.0188	$1,049.01	$1,049.00	$1,049.00