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	$239.27	4.259%	$249.4605	$249.46	$249.45	$249.50
Purchase #2	$170.88	8.654%	$185.668	$185.67	$185.65	$185.70
Purchase #3	$199.53	8.671%	$216.8312	$216.83	$216.85	$216.80
Purchase #4	$39.65	13.316%	$44.9298	$44.93	$44.95	$44.90
Purchase #5	$56.73	8.273%	$61.4233	$61.42	$61.40	$61.40
Purchase #6	$55.32	7.435%	$59.433	$59.43	$59.45	$59.40
Purchase #7	$213.52	5.805%	$225.9148	$225.91	$225.90	$225.90
7 purchase totals =	$974.90		$1,043.6606	$1,043.65	$1,043.65	$1,043.60