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	$73.78	10.614%	$81.611	$81.61	$81.60	$81.60
Purchase #2	$185.59	5.300%	$195.4263	$195.43	$195.45	$195.40
Purchase #3	$87.95	6.767%	$93.9016	$93.90	$93.90	$93.90
Purchase #4	$139.97	8.531%	$151.9108	$151.91	$151.90	$151.90
Purchase #5	$120.87	5.780%	$127.8563	$127.86	$127.85	$127.90
Purchase #6	$186.52	11.739%	$208.4156	$208.42	$208.40	$208.40
Purchase #7	$173.70	11.620%	$193.8839	$193.88	$193.90	$193.90
7 purchase totals =	$968.38		$1,053.0055	$1,053.01	$1,053.00	$1,053.00