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	$67.65	5.250%	$71.2016	$71.20	$71.20	$71.20
Purchase #2	$59.48	13.627%	$67.5853	$67.59	$67.60	$67.60
Purchase #3	$152.30	10.865%	$168.8474	$168.85	$168.85	$168.80
Purchase #4	$108.93	3.620%	$112.8733	$112.87	$112.85	$112.90
Purchase #5	$144.91	5.366%	$152.6859	$152.69	$152.70	$152.70
Purchase #6	$227.84	13.387%	$258.3409	$258.34	$258.35	$258.30
Purchase #7	$182.25	6.754%	$194.5592	$194.56	$194.55	$194.60
7 purchase totals =	$943.36		$1,026.0936	$1,026.10	$1,026.10	$1,026.10