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	$96.59	13.407%	$109.5398	$109.54	$109.55	$109.50
Purchase #2	$186.38	9.569%	$204.2147	$204.21	$204.20	$204.20
Purchase #3	$35.84	13.565%	$40.7017	$40.70	$40.70	$40.70
Purchase #4	$186.54	7.606%	$200.7282	$200.73	$200.75	$200.70
Purchase #5	$50.77	12.447%	$57.0893	$57.09	$57.10	$57.10
Purchase #6	$250.52	9.845%	$275.1837	$275.18	$275.20	$275.20
Purchase #7	$112.39	3.635%	$116.4754	$116.48	$116.50	$116.50
7 purchase totals =	$919.03		$1,003.9328	$1,003.93	$1,004.00	$1,003.90