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	$137.86	13.242%	$156.1154	$156.12	$156.10	$156.10
Purchase #2	$213.74	4.278%	$222.8838	$222.88	$222.90	$222.90
Purchase #3	$85.88	13.410%	$97.3965	$97.40	$97.40	$97.40
Purchase #4	$142.42	13.201%	$161.2209	$161.22	$161.20	$161.20
Purchase #5	$206.47	4.544%	$215.852	$215.85	$215.85	$215.90
Purchase #6	$205.69	6.639%	$219.3458	$219.35	$219.35	$219.30
Purchase #7	$67.71	6.382%	$72.0313	$72.03	$72.05	$72.00
7 purchase totals =	$1,059.77		$1,144.8457	$1,144.85	$1,144.85	$1,144.80