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	$223.40	3.625%	$231.4983	$231.50	$231.50	$231.50
Purchase #2	$94.74	11.393%	$105.5337	$105.53	$105.55	$105.50
Purchase #3	$142.36	12.623%	$160.3301	$160.33	$160.35	$160.30
Purchase #4	$69.45	12.620%	$78.2146	$78.21	$78.20	$78.20
Purchase #5	$212.49	6.720%	$226.7693	$226.77	$226.75	$226.80
Purchase #6	$215.89	8.643%	$234.5494	$234.55	$234.55	$234.50
Purchase #7	$249.94	12.151%	$280.3102	$280.31	$280.30	$280.30
7 purchase totals =	$1,208.27		$1,317.2056	$1,317.20	$1,317.20	$1,317.10