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	$243.31	8.231%	$263.3368	$263.34	$263.35	$263.30
Purchase #2	$133.78	7.377%	$143.649	$143.65	$143.65	$143.60
Purchase #3	$12.69	3.405%	$13.1221	$13.12	$13.10	$13.10
Purchase #4	$24.34	13.416%	$27.6055	$27.61	$27.60	$27.60
Purchase #5	$140.81	8.801%	$153.2027	$153.20	$153.20	$153.20
Purchase #6	$236.78	11.424%	$263.8297	$263.83	$263.85	$263.80
Purchase #7	$142.96	5.506%	$150.8314	$150.83	$150.85	$150.80
7 purchase totals =	$934.67		$1,015.5772	$1,015.58	$1,015.60	$1,015.40