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	$96.39	6.504%	$102.6592	$102.66	$102.65	$102.70
Purchase #2	$161.81	10.277%	$178.4392	$178.44	$178.45	$178.40
Purchase #3	$249.99	12.387%	$280.9563	$280.96	$280.95	$281.00
Purchase #4	$186.27	9.553%	$204.0644	$204.06	$204.05	$204.10
Purchase #5	$82.94	9.111%	$90.4967	$90.50	$90.50	$90.50
Purchase #6	$172.73	13.820%	$196.6013	$196.60	$196.60	$196.60
Purchase #7	$88.29	12.306%	$99.155	$99.16	$99.15	$99.20
7 purchase totals =	$1,038.42		$1,152.3721	$1,152.38	$1,152.35	$1,152.50