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	$207.75	10.563%	$229.6946	$229.69	$229.70	$229.70
Purchase #2	$12.40	12.558%	$13.9572	$13.96	$13.95	$14.00
Purchase #3	$37.87	13.641%	$43.0358	$43.04	$43.05	$43.00
Purchase #4	$52.91	4.118%	$55.0888	$55.09	$55.10	$55.10
Purchase #5	$89.53	7.791%	$96.5053	$96.51	$96.50	$96.50
Purchase #6	$31.38	3.794%	$32.5706	$32.57	$32.55	$32.60
Purchase #7	$30.31	8.372%	$32.8476	$32.85	$32.85	$32.80
7 purchase totals =	$462.15		$503.6999	$503.71	$503.70	$503.70