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	$147.84	8.432%	$160.3059	$160.31	$160.30	$160.30
Purchase #2	$224.82	13.116%	$254.3074	$254.31	$254.30	$254.30
Purchase #3	$207.89	5.724%	$219.7896	$219.79	$219.80	$219.80
Purchase #4	$206.94	11.676%	$231.1023	$231.10	$231.10	$231.10
Purchase #5	$52.98	9.577%	$58.0539	$58.05	$58.05	$58.10
Purchase #6	$102.39	8.849%	$111.4505	$111.45	$111.45	$111.50
Purchase #7	$25.44	13.518%	$28.879	$28.88	$28.90	$28.90
7 purchase totals =	$968.30		$1,063.8886	$1,063.89	$1,063.90	$1,064.00