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	$47.92	12.158%	$53.7461	$53.75	$53.75	$53.70
Purchase #2	$26.86	7.567%	$28.8925	$28.89	$28.90	$28.90
Purchase #3	$167.57	3.802%	$173.941	$173.94	$173.95	$173.90
Purchase #4	$133.84	4.301%	$139.5965	$139.60	$139.60	$139.60
Purchase #5	$238.66	9.387%	$261.063	$261.06	$261.05	$261.10
Purchase #6	$215.93	12.492%	$242.904	$242.90	$242.90	$242.90
Purchase #7	$199.88	13.611%	$227.0857	$227.09	$227.10	$227.10
7 purchase totals =	$1,030.66		$1,127.2288	$1,127.23	$1,127.25	$1,127.20