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	$82.54	5.391%	$86.9897	$86.99	$87.00	$87.00
Purchase #2	$83.59	7.236%	$89.6386	$89.64	$89.65	$89.60
Purchase #3	$36.69	13.831%	$41.7646	$41.76	$41.75	$41.80
Purchase #4	$33.90	7.813%	$36.5486	$36.55	$36.55	$36.50
Purchase #5	$158.94	3.425%	$164.3837	$164.38	$164.40	$164.40
Purchase #6	$49.30	7.173%	$52.8363	$52.84	$52.85	$52.80
Purchase #7	$171.30	5.589%	$180.874	$180.87	$180.85	$180.90
7 purchase totals =	$616.26		$653.0355	$653.03	$653.05	$653.00