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	$24.91	3.429%	$25.7642	$25.76	$25.75	$25.80
Purchase #2	$31.97	3.558%	$33.1075	$33.11	$33.10	$33.10
Purchase #3	$229.53	5.195%	$241.4541	$241.45	$241.45	$241.50
Purchase #4	$56.28	5.429%	$59.3354	$59.34	$59.35	$59.30
Purchase #5	$220.34	11.715%	$246.1528	$246.15	$246.15	$246.20
Purchase #6	$208.35	4.254%	$217.2132	$217.21	$217.20	$217.20
Purchase #7	$47.54	11.241%	$52.884	$52.88	$52.90	$52.90
7 purchase totals =	$818.92		$875.9112	$875.90	$875.90	$876.00