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	$244.71	7.482%	$263.0192	$263.02	$263.00	$263.00
Purchase #2	$102.49	11.812%	$114.5961	$114.60	$114.60	$114.60
Purchase #3	$250.72	12.560%	$282.2104	$282.21	$282.20	$282.20
Purchase #4	$63.52	13.819%	$72.2978	$72.30	$72.30	$72.30
Purchase #5	$83.96	3.295%	$86.7265	$86.73	$86.75	$86.70
Purchase #6	$246.73	13.756%	$280.6702	$280.67	$280.65	$280.70
Purchase #7	$159.77	13.236%	$180.9172	$180.92	$180.90	$180.90
7 purchase totals =	$1,151.90		$1,280.4374	$1,280.45	$1,280.40	$1,280.40