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	$157.50	12.154%	$176.6426	$176.64	$176.65	$176.60
Purchase #2	$169.41	5.399%	$178.5564	$178.56	$178.55	$178.60
Purchase #3	$90.94	8.287%	$98.4762	$98.48	$98.50	$98.50
Purchase #4	$105.62	8.445%	$114.5396	$114.54	$114.55	$114.50
Purchase #5	$75.57	9.648%	$82.861	$82.86	$82.85	$82.90
Purchase #6	$66.87	7.786%	$72.0765	$72.08	$72.10	$72.10
Purchase #7	$29.34	9.420%	$32.1038	$32.10	$32.10	$32.10
7 purchase totals =	$695.25		$755.2561	$755.26	$755.30	$755.30