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	$42.65	11.482%	$47.5471	$47.55	$47.55	$47.50
Purchase #2	$225.49	13.129%	$255.0946	$255.09	$255.10	$255.10
Purchase #3	$8.43	3.674%	$8.7397	$8.74	$8.75	$8.70
Purchase #4	$195.69	10.727%	$216.6817	$216.68	$216.70	$216.70
Purchase #5	$56.92	3.745%	$59.0517	$59.05	$59.05	$59.10
Purchase #6	$153.88	9.624%	$168.6894	$168.69	$168.70	$168.70
Purchase #7	$52.51	4.127%	$54.6771	$54.68	$54.70	$54.70
7 purchase totals =	$735.57		$810.4813	$810.48	$810.55	$810.50