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	$184.46	13.379%	$209.1389	$209.14	$209.15	$209.10
Purchase #2	$202.67	11.318%	$225.6082	$225.61	$225.60	$225.60
Purchase #3	$202.75	9.517%	$222.0457	$222.05	$222.05	$222.00
Purchase #4	$168.89	7.170%	$180.9994	$181.00	$181.00	$181.00
Purchase #5	$145.86	6.759%	$155.7187	$155.72	$155.70	$155.70
Purchase #6	$210.95	5.242%	$222.008	$222.01	$222.00	$222.00
Purchase #7	$145.34	13.164%	$164.4726	$164.47	$164.45	$164.50
7 purchase totals =	$1,260.92		$1,379.9915	$1,380.00	$1,379.95	$1,379.90