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	$240.50	4.217%	$250.6419	$250.64	$250.65	$250.60
Purchase #2	$205.56	3.807%	$213.3857	$213.39	$213.40	$213.40
Purchase #3	$48.51	13.468%	$55.0433	$55.04	$55.05	$55.00
Purchase #4	$173.87	6.529%	$185.222	$185.22	$185.20	$185.20
Purchase #5	$22.54	7.768%	$24.2909	$24.29	$24.30	$24.30
Purchase #6	$187.82	3.845%	$195.0417	$195.04	$195.05	$195.00
Purchase #7	$72.97	7.411%	$78.3778	$78.38	$78.40	$78.40
7 purchase totals =	$951.77		$1,002.0033	$1,002.00	$1,002.05	$1,001.90