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	$103.55	5.870%	$109.6284	$109.63	$109.65	$109.60
Purchase #2	$83.61	3.265%	$86.3399	$86.34	$86.35	$86.30
Purchase #3	$246.94	3.479%	$255.531	$255.53	$255.55	$255.50
Purchase #4	$137.62	10.267%	$151.7494	$151.75	$151.75	$151.70
Purchase #5	$42.28	10.644%	$46.7803	$46.78	$46.80	$46.80
Purchase #6	$231.69	11.813%	$259.0595	$259.06	$259.05	$259.10
Purchase #7	$25.81	7.683%	$27.793	$27.79	$27.80	$27.80
7 purchase totals =	$871.50		$936.8815	$936.88	$936.95	$936.80