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	$238.50	3.563%	$246.9978	$247.00	$247.00	$247.00
Purchase #2	$147.46	13.590%	$167.4998	$167.50	$167.50	$167.50
Purchase #3	$190.57	4.635%	$199.4029	$199.40	$199.40	$199.40
Purchase #4	$85.71	4.777%	$89.8044	$89.80	$89.80	$89.80
Purchase #5	$49.60	9.800%	$54.4608	$54.46	$54.45	$54.50
Purchase #6	$245.25	5.360%	$258.3954	$258.40	$258.40	$258.40
Purchase #7	$146.79	9.603%	$160.8862	$160.89	$160.90	$160.90
7 purchase totals =	$1,103.88		$1,177.4473	$1,177.45	$1,177.45	$1,177.50