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	$80.77	9.305%	$88.2856	$88.29	$88.30	$88.30
Purchase #2	$18.25	12.297%	$20.4942	$20.49	$20.50	$20.50
Purchase #3	$62.63	6.259%	$66.55	$66.55	$66.55	$66.60
Purchase #4	$134.87	5.736%	$142.6061	$142.61	$142.60	$142.60
Purchase #5	$185.90	5.849%	$196.7733	$196.77	$196.75	$196.80
Purchase #6	$249.81	9.592%	$273.7718	$273.77	$273.75	$273.80
Purchase #7	$170.89	4.538%	$178.645	$178.65	$178.65	$178.60
7 purchase totals =	$903.12		$967.1260	$967.13	$967.10	$967.20