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	$41.83	4.696%	$43.7943	$43.79	$43.80	$43.80
Purchase #2	$178.25	10.468%	$196.9092	$196.91	$196.90	$196.90
Purchase #3	$98.68	10.405%	$108.9477	$108.95	$108.95	$108.90
Purchase #4	$69.55	8.489%	$75.4541	$75.45	$75.45	$75.50
Purchase #5	$32.87	12.277%	$36.9054	$36.91	$36.90	$36.90
Purchase #6	$28.26	4.416%	$29.508	$29.51	$29.50	$29.50
Purchase #7	$69.37	3.114%	$71.5302	$71.53	$71.55	$71.50
7 purchase totals =	$518.81		$563.0489	$563.05	$563.05	$563.00