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	$201.57	10.361%	$222.4547	$222.45	$222.45	$222.50
Purchase #2	$90.27	8.687%	$98.1118	$98.11	$98.10	$98.10
Purchase #3	$143.46	6.654%	$153.0058	$153.01	$153.00	$153.00
Purchase #4	$19.82	10.418%	$21.8848	$21.88	$21.90	$21.90
Purchase #5	$29.81	5.775%	$31.5315	$31.53	$31.55	$31.50
Purchase #6	$197.71	12.772%	$222.9615	$222.96	$222.95	$223.00
Purchase #7	$103.98	8.555%	$112.8755	$112.88	$112.90	$112.90
7 purchase totals =	$786.62		$862.8256	$862.82	$862.85	$862.90