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	$229.34	11.453%	$255.6063	$255.61	$255.60	$255.60
Purchase #2	$90.87	10.741%	$100.6303	$100.63	$100.65	$100.60
Purchase #3	$104.39	10.242%	$115.0816	$115.08	$115.10	$115.10
Purchase #4	$213.29	12.112%	$239.1237	$239.12	$239.10	$239.10
Purchase #5	$48.67	12.273%	$54.6433	$54.64	$54.65	$54.60
Purchase #6	$177.89	3.519%	$184.1499	$184.15	$184.15	$184.10
Purchase #7	$219.40	8.811%	$238.7313	$238.73	$238.75	$238.70
7 purchase totals =	$1,083.85		$1,187.9664	$1,187.96	$1,188.00	$1,187.80