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	$78.38	12.708%	$88.3405	$88.34	$88.35	$88.30
Purchase #2	$133.71	6.661%	$142.6164	$142.62	$142.60	$142.60
Purchase #3	$205.71	5.159%	$216.3226	$216.32	$216.30	$216.30
Purchase #4	$157.88	5.782%	$167.0086	$167.01	$167.00	$167.00
Purchase #5	$215.54	6.381%	$229.2936	$229.29	$229.30	$229.30
Purchase #6	$161.44	4.196%	$168.214	$168.21	$168.20	$168.20
Purchase #7	$44.79	5.661%	$47.3256	$47.33	$47.35	$47.30
7 purchase totals =	$997.45		$1,059.1213	$1,059.12	$1,059.10	$1,059.00