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	$212.94	5.430%	$224.5026	$224.50	$224.50	$224.50
Purchase #2	$212.47	5.783%	$224.7571	$224.76	$224.75	$224.80
Purchase #3	$54.43	3.822%	$56.5103	$56.51	$56.50	$56.50
Purchase #4	$30.25	3.558%	$31.3263	$31.33	$31.35	$31.30
Purchase #5	$248.60	12.639%	$280.0206	$280.02	$280.00	$280.00
Purchase #6	$86.28	7.184%	$92.4784	$92.48	$92.50	$92.50
Purchase #7	$49.89	11.618%	$55.6862	$55.69	$55.70	$55.70
7 purchase totals =	$894.86		$965.2815	$965.29	$965.30	$965.30