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	$163.52	13.850%	$186.1675	$186.17	$186.15	$186.20
Purchase #2	$114.94	10.523%	$127.0351	$127.04	$127.05	$127.00
Purchase #3	$214.59	3.643%	$222.4075	$222.41	$222.40	$222.40
Purchase #4	$249.53	12.253%	$280.1049	$280.10	$280.10	$280.10
Purchase #5	$242.75	4.797%	$254.3947	$254.39	$254.40	$254.40
Purchase #6	$237.41	3.764%	$246.3461	$246.35	$246.35	$246.30
Purchase #7	$82.56	9.316%	$90.2513	$90.25	$90.25	$90.30
7 purchase totals =	$1,305.30		$1,406.7071	$1,406.71	$1,406.70	$1,406.70