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	$237.29	9.197%	$259.1136	$259.11	$259.10	$259.10
Purchase #2	$75.51	13.174%	$85.4577	$85.46	$85.45	$85.50
Purchase #3	$106.78	13.185%	$120.8589	$120.86	$120.85	$120.90
Purchase #4	$236.48	3.727%	$245.2936	$245.29	$245.30	$245.30
Purchase #5	$198.83	12.758%	$224.1967	$224.20	$224.20	$224.20
Purchase #6	$196.35	13.113%	$222.0974	$222.10	$222.10	$222.10
Purchase #7	$38.48	7.464%	$41.3521	$41.35	$41.35	$41.40
7 purchase totals =	$1,089.72		$1,198.3700	$1,198.37	$1,198.35	$1,198.50