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	$96.78	12.683%	$109.0546	$109.05	$109.05	$109.10
Purchase #2	$230.90	13.863%	$262.9097	$262.91	$262.90	$262.90
Purchase #3	$182.35	11.493%	$203.3075	$203.31	$203.30	$203.30
Purchase #4	$41.73	5.201%	$43.9004	$43.90	$43.90	$43.90
Purchase #5	$221.75	7.638%	$238.6873	$238.69	$238.70	$238.70
Purchase #6	$231.45	13.635%	$263.0082	$263.01	$263.00	$263.00
Purchase #7	$74.43	10.525%	$82.2638	$82.26	$82.25	$82.30
7 purchase totals =	$1,079.39		$1,203.1315	$1,203.13	$1,203.10	$1,203.20