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	$217.25	6.374%	$231.0975	$231.10	$231.10	$231.10
Purchase #2	$193.25	9.507%	$211.6223	$211.62	$211.60	$211.60
Purchase #3	$166.34	10.143%	$183.2119	$183.21	$183.20	$183.20
Purchase #4	$223.70	6.591%	$238.4441	$238.44	$238.45	$238.40
Purchase #5	$155.94	4.480%	$162.9261	$162.93	$162.95	$162.90
Purchase #6	$71.61	10.238%	$78.9414	$78.94	$78.95	$78.90
Purchase #7	$245.64	13.364%	$278.4673	$278.47	$278.45	$278.50
7 purchase totals =	$1,273.73		$1,384.7106	$1,384.71	$1,384.70	$1,384.60