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	$59.32	5.546%	$62.6099	$62.61	$62.60	$62.60
Purchase #2	$56.51	11.279%	$62.8838	$62.88	$62.90	$62.90
Purchase #3	$94.70	12.724%	$106.7496	$106.75	$106.75	$106.70
Purchase #4	$59.63	7.709%	$64.2269	$64.23	$64.25	$64.20
Purchase #5	$96.58	13.803%	$109.9109	$109.91	$109.90	$109.90
Purchase #6	$176.36	11.473%	$196.5938	$196.59	$196.60	$196.60
Purchase #7	$228.35	10.555%	$252.4523	$252.45	$252.45	$252.50
7 purchase totals =	$771.45		$855.4272	$855.42	$855.45	$855.40