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	$135.58	4.390%	$141.532	$141.53	$141.55	$141.50
Purchase #2	$94.93	7.215%	$101.7792	$101.78	$101.80	$101.80
Purchase #3	$176.79	6.575%	$188.4139	$188.41	$188.40	$188.40
Purchase #4	$191.92	11.347%	$213.6972	$213.70	$213.70	$213.70
Purchase #5	$94.88	3.568%	$98.2653	$98.27	$98.25	$98.30
Purchase #6	$235.31	8.836%	$256.102	$256.10	$256.10	$256.10
Purchase #7	$57.55	13.787%	$65.4844	$65.48	$65.50	$65.50
7 purchase totals =	$986.96		$1,065.2740	$1,065.27	$1,065.30	$1,065.30