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	$243.70	6.508%	$259.56	$259.56	$259.55	$259.60
Purchase #2	$91.56	3.256%	$94.5412	$94.54	$94.55	$94.50
Purchase #3	$218.53	8.198%	$236.4451	$236.45	$236.45	$236.40
Purchase #4	$245.36	12.864%	$276.9231	$276.92	$276.90	$276.90
Purchase #5	$223.52	7.783%	$240.9166	$240.92	$240.90	$240.90
Purchase #6	$56.60	4.715%	$59.2687	$59.27	$59.25	$59.30
Purchase #7	$51.44	10.680%	$56.9338	$56.93	$56.95	$56.90
7 purchase totals =	$1,130.71		$1,224.5885	$1,224.59	$1,224.55	$1,224.50