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	$164.41	13.557%	$186.6991	$186.70	$186.70	$186.70
Purchase #2	$125.92	4.741%	$131.8899	$131.89	$131.90	$131.90
Purchase #3	$131.69	5.580%	$139.0383	$139.04	$139.05	$139.00
Purchase #4	$176.57	13.291%	$200.0379	$200.04	$200.05	$200.00
Purchase #5	$154.29	7.798%	$166.3215	$166.32	$166.30	$166.30
Purchase #6	$26.47	7.170%	$28.3679	$28.37	$28.35	$28.40
Purchase #7	$98.69	3.829%	$102.4688	$102.47	$102.45	$102.50
7 purchase totals =	$878.04		$954.8234	$954.83	$954.80	$954.80