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	$148.29	5.364%	$156.2443	$156.24	$156.25	$156.20
Purchase #2	$77.53	5.387%	$81.7065	$81.71	$81.70	$81.70
Purchase #3	$34.86	10.228%	$38.4255	$38.43	$38.45	$38.40
Purchase #4	$78.88	13.284%	$89.3584	$89.36	$89.35	$89.40
Purchase #5	$59.64	5.523%	$62.9339	$62.93	$62.95	$62.90
Purchase #6	$119.46	3.457%	$123.5897	$123.59	$123.60	$123.60
Purchase #7	$112.30	5.874%	$118.8965	$118.90	$118.90	$118.90
7 purchase totals =	$630.96		$671.1548	$671.16	$671.20	$671.10