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	$92.88	13.482%	$105.4021	$105.40	$105.40	$105.40
Purchase #2	$124.63	12.339%	$140.0081	$140.01	$140.00	$140.00
Purchase #3	$223.78	8.708%	$243.2668	$243.27	$243.25	$243.30
Purchase #4	$152.99	10.319%	$168.777	$168.78	$168.80	$168.80
Purchase #5	$134.56	5.595%	$142.0886	$142.09	$142.10	$142.10
Purchase #6	$132.29	13.639%	$150.333	$150.33	$150.35	$150.30
Purchase #7	$49.74	13.660%	$56.5345	$56.53	$56.55	$56.50
7 purchase totals =	$910.87		$1,006.4101	$1,006.41	$1,006.45	$1,006.40