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	$57.45	13.741%	$65.3442	$65.34	$65.35	$65.30
Purchase #2	$29.75	11.488%	$33.1677	$33.17	$33.15	$33.20
Purchase #3	$193.61	5.307%	$203.8849	$203.88	$203.90	$203.90
Purchase #4	$13.69	5.225%	$14.4053	$14.41	$14.40	$14.40
Purchase #5	$90.59	13.821%	$103.1104	$103.11	$103.10	$103.10
Purchase #6	$48.44	7.108%	$51.8831	$51.88	$51.90	$51.90
Purchase #7	$59.49	6.277%	$63.2242	$63.22	$63.20	$63.20
7 purchase totals =	$493.02		$535.0198	$535.01	$535.00	$535.00