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	$22.70	12.753%	$25.5949	$25.59	$25.60	$25.60
Purchase #2	$71.74	5.267%	$75.5185	$75.52	$75.50	$75.50
Purchase #3	$216.38	6.862%	$231.228	$231.23	$231.25	$231.20
Purchase #4	$185.72	5.566%	$196.0572	$196.06	$196.05	$196.10
Purchase #5	$22.90	11.290%	$25.4854	$25.49	$25.50	$25.50
Purchase #6	$69.38	4.219%	$72.3071	$72.31	$72.30	$72.30
Purchase #7	$121.74	7.776%	$131.2065	$131.21	$131.20	$131.20
7 purchase totals =	$710.56		$757.3976	$757.41	$757.40	$757.40