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	$212.37	10.152%	$233.9298	$233.93	$233.95	$233.90
Purchase #2	$40.41	12.840%	$45.5986	$45.60	$45.60	$45.60
Purchase #3	$83.96	13.191%	$95.0352	$95.04	$95.05	$95.00
Purchase #4	$23.72	9.289%	$25.9234	$25.92	$25.90	$25.90
Purchase #5	$115.34	3.646%	$119.5453	$119.55	$119.55	$119.50
Purchase #6	$105.36	13.379%	$119.4561	$119.46	$119.45	$119.50
Purchase #7	$67.84	8.242%	$73.4314	$73.43	$73.45	$73.40
7 purchase totals =	$649.00		$712.9198	$712.93	$712.95	$712.80