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	$57.81	6.284%	$61.4428	$61.44	$61.45	$61.40
Purchase #2	$37.92	8.136%	$41.0052	$41.01	$41.00	$41.00
Purchase #3	$73.98	11.665%	$82.6098	$82.61	$82.60	$82.60
Purchase #4	$108.69	8.170%	$117.57	$117.57	$117.55	$117.60
Purchase #5	$7.99	10.736%	$8.8478	$8.85	$8.85	$8.80
Purchase #6	$216.34	11.751%	$241.7621	$241.76	$241.75	$241.80
Purchase #7	$56.96	8.741%	$61.9389	$61.94	$61.95	$61.90
7 purchase totals =	$559.69		$615.1766	$615.18	$615.15	$615.10