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	$8.51	13.366%	$9.6474	$9.65	$9.65	$9.60
Purchase #2	$173.57	12.637%	$195.504	$195.50	$195.50	$195.50
Purchase #3	$76.63	7.521%	$82.3933	$82.39	$82.40	$82.40
Purchase #4	$37.39	8.317%	$40.4997	$40.50	$40.50	$40.50
Purchase #5	$134.41	12.207%	$150.8174	$150.82	$150.80	$150.80
Purchase #6	$110.91	5.125%	$116.5941	$116.59	$116.60	$116.60
Purchase #7	$176.41	7.215%	$189.138	$189.14	$189.15	$189.10
7 purchase totals =	$717.83		$784.5939	$784.59	$784.60	$784.50