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	$230.64	5.768%	$243.9433	$243.94	$243.95	$243.90
Purchase #2	$43.67	7.222%	$46.8238	$46.82	$46.80	$46.80
Purchase #3	$30.56	6.324%	$32.4926	$32.49	$32.50	$32.50
Purchase #4	$30.43	8.563%	$33.0357	$33.04	$33.05	$33.00
Purchase #5	$103.34	6.304%	$109.8546	$109.85	$109.85	$109.90
Purchase #6	$226.34	7.649%	$243.6527	$243.65	$243.65	$243.70
Purchase #7	$147.59	6.204%	$156.7465	$156.75	$156.75	$156.70
7 purchase totals =	$812.57		$866.5492	$866.54	$866.55	$866.50