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	$135.53	12.755%	$152.8169	$152.82	$152.80	$152.80
Purchase #2	$154.59	9.674%	$169.545	$169.55	$169.55	$169.50
Purchase #3	$89.95	8.786%	$97.853	$97.85	$97.85	$97.90
Purchase #4	$122.71	6.672%	$130.8972	$130.90	$130.90	$130.90
Purchase #5	$76.58	10.183%	$84.3781	$84.38	$84.40	$84.40
Purchase #6	$248.78	12.794%	$280.6089	$280.61	$280.60	$280.60
Purchase #7	$67.46	5.594%	$71.2337	$71.23	$71.25	$71.20
7 purchase totals =	$895.60		$987.3328	$987.34	$987.35	$987.30