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	$75.32	8.268%	$81.5475	$81.55	$81.55	$81.50
Purchase #2	$55.98	3.363%	$57.8626	$57.86	$57.85	$57.90
Purchase #3	$232.46	6.462%	$247.4816	$247.48	$247.50	$247.50
Purchase #4	$244.88	5.571%	$258.5223	$258.52	$258.50	$258.50
Purchase #5	$84.62	6.300%	$89.9511	$89.95	$89.95	$90.00
Purchase #6	$139.69	7.671%	$150.4056	$150.41	$150.40	$150.40
Purchase #7	$186.89	7.858%	$201.5758	$201.58	$201.60	$201.60
7 purchase totals =	$1,019.84		$1,087.3465	$1,087.35	$1,087.35	$1,087.40