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	$185.54	4.336%	$193.585	$193.59	$193.60	$193.60
Purchase #2	$69.90	10.819%	$77.4625	$77.46	$77.45	$77.50
Purchase #3	$247.27	13.859%	$281.5391	$281.54	$281.55	$281.50
Purchase #4	$165.86	12.373%	$186.3819	$186.38	$186.40	$186.40
Purchase #5	$38.31	6.182%	$40.6783	$40.68	$40.70	$40.70
Purchase #6	$173.65	7.417%	$186.5296	$186.53	$186.55	$186.50
Purchase #7	$148.78	8.151%	$160.9071	$160.91	$160.90	$160.90
7 purchase totals =	$1,029.31		$1,127.0835	$1,127.09	$1,127.15	$1,127.10