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	$246.55	3.497%	$255.1719	$255.17	$255.15	$255.20
Purchase #2	$210.28	9.209%	$229.6447	$229.64	$229.65	$229.60
Purchase #3	$119.30	3.127%	$123.0305	$123.03	$123.05	$123.00
Purchase #4	$86.55	12.561%	$97.4215	$97.42	$97.40	$97.40
Purchase #5	$66.96	6.161%	$71.0854	$71.09	$71.10	$71.10
Purchase #6	$162.42	4.127%	$169.1231	$169.12	$169.10	$169.10
Purchase #7	$218.48	10.540%	$241.5078	$241.51	$241.50	$241.50
7 purchase totals =	$1,110.54		$1,186.9849	$1,186.98	$1,186.95	$1,186.90