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	$96.39	9.184%	$105.2425	$105.24	$105.25	$105.20
Purchase #2	$237.89	7.581%	$255.9244	$255.92	$255.90	$255.90
Purchase #3	$44.79	11.693%	$50.0273	$50.03	$50.05	$50.00
Purchase #4	$112.89	8.255%	$122.2091	$122.21	$122.20	$122.20
Purchase #5	$204.77	4.452%	$213.8864	$213.89	$213.90	$213.90
Purchase #6	$203.86	3.665%	$211.3315	$211.33	$211.35	$211.30
Purchase #7	$229.79	3.377%	$237.55	$237.55	$237.55	$237.60
7 purchase totals =	$1,130.38		$1,196.1712	$1,196.17	$1,196.20	$1,196.10