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	$198.89	13.610%	$225.9589	$225.96	$225.95	$226.00
Purchase #2	$30.66	6.344%	$32.6051	$32.61	$32.60	$32.60
Purchase #3	$94.51	3.449%	$97.7696	$97.77	$97.75	$97.80
Purchase #4	$150.95	3.553%	$156.3133	$156.31	$156.30	$156.30
Purchase #5	$223.38	7.291%	$239.6666	$239.67	$239.65	$239.70
Purchase #6	$47.60	9.294%	$52.0239	$52.02	$52.00	$52.00
Purchase #7	$38.98	3.846%	$40.4792	$40.48	$40.50	$40.50
7 purchase totals =	$784.97		$844.8166	$844.82	$844.75	$844.90