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	$59.31	5.258%	$62.4285	$62.43	$62.45	$62.40
Purchase #2	$121.27	3.745%	$125.8116	$125.81	$125.80	$125.80
Purchase #3	$245.88	4.637%	$257.2815	$257.28	$257.30	$257.30
Purchase #4	$112.93	12.840%	$127.4302	$127.43	$127.45	$127.40
Purchase #5	$142.47	13.109%	$161.1464	$161.15	$161.15	$161.10
Purchase #6	$157.73	13.859%	$179.5898	$179.59	$179.60	$179.60
Purchase #7	$245.31	12.421%	$275.78	$275.78	$275.80	$275.80
7 purchase totals =	$1,084.90		$1,189.4680	$1,189.47	$1,189.55	$1,189.40