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	$118.82	6.768%	$126.8617	$126.86	$126.85	$126.90
Purchase #2	$39.61	5.748%	$41.8868	$41.89	$41.90	$41.90
Purchase #3	$183.39	6.636%	$195.5598	$195.56	$195.55	$195.60
Purchase #4	$172.63	13.860%	$196.5565	$196.56	$196.55	$196.60
Purchase #5	$59.79	7.688%	$64.3867	$64.39	$64.40	$64.40
Purchase #6	$135.53	11.608%	$151.2623	$151.26	$151.25	$151.30
Purchase #7	$74.85	9.538%	$81.9892	$81.99	$82.00	$82.00
7 purchase totals =	$784.62		$858.5030	$858.51	$858.50	$858.70