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	$137.57	10.848%	$152.4936	$152.49	$152.50	$152.50
Purchase #2	$158.65	7.700%	$170.8661	$170.87	$170.85	$170.90
Purchase #3	$230.47	3.193%	$237.8289	$237.83	$237.85	$237.80
Purchase #4	$97.87	7.591%	$105.2993	$105.30	$105.30	$105.30
Purchase #5	$116.75	9.276%	$127.5797	$127.58	$127.60	$127.60
Purchase #6	$151.33	5.619%	$159.8332	$159.83	$159.85	$159.80
Purchase #7	$86.90	3.260%	$89.7329	$89.73	$89.75	$89.70
7 purchase totals =	$979.54		$1,043.6337	$1,043.63	$1,043.70	$1,043.60