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	$209.83	13.450%	$238.0521	$238.05	$238.05	$238.10
Purchase #2	$18.47	5.397%	$19.4668	$19.47	$19.45	$19.50
Purchase #3	$203.74	8.498%	$221.0538	$221.05	$221.05	$221.10
Purchase #4	$223.73	8.141%	$241.9439	$241.94	$241.95	$241.90
Purchase #5	$133.39	7.419%	$143.2862	$143.29	$143.30	$143.30
Purchase #6	$80.89	5.527%	$85.3608	$85.36	$85.35	$85.40
Purchase #7	$242.78	12.300%	$272.6419	$272.64	$272.65	$272.60
7 purchase totals =	$1,112.83		$1,221.8055	$1,221.80	$1,221.80	$1,221.90