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	$131.61	7.832%	$141.9177	$141.92	$141.90	$141.90
Purchase #2	$178.50	11.210%	$198.5099	$198.51	$198.50	$198.50
Purchase #3	$92.64	7.172%	$99.2841	$99.28	$99.30	$99.30
Purchase #4	$206.62	5.313%	$217.5977	$217.60	$217.60	$217.60
Purchase #5	$226.91	12.724%	$255.782	$255.78	$255.80	$255.80
Purchase #6	$53.57	11.305%	$59.6261	$59.63	$59.65	$59.60
Purchase #7	$121.61	12.788%	$137.1615	$137.16	$137.15	$137.20
7 purchase totals =	$1,011.46		$1,109.8790	$1,109.88	$1,109.90	$1,109.90