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	$82.43	12.130%	$92.4288	$92.43	$92.45	$92.40
Purchase #2	$150.89	7.607%	$162.3682	$162.37	$162.35	$162.40
Purchase #3	$230.76	7.782%	$248.7177	$248.72	$248.70	$248.70
Purchase #4	$77.78	11.329%	$86.5917	$86.59	$86.60	$86.60
Purchase #5	$43.54	12.546%	$49.0025	$49.00	$49.00	$49.00
Purchase #6	$43.78	6.290%	$46.5338	$46.53	$46.55	$46.50
Purchase #7	$82.81	13.313%	$93.8345	$93.83	$93.85	$93.80
7 purchase totals =	$711.99		$779.4772	$779.47	$779.50	$779.40