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	$72.42	13.354%	$82.091	$82.09	$82.10	$82.10
Purchase #2	$41.30	8.763%	$44.9191	$44.92	$44.90	$44.90
Purchase #3	$162.58	12.803%	$183.3951	$183.40	$183.40	$183.40
Purchase #4	$240.61	13.151%	$272.2526	$272.25	$272.25	$272.30
Purchase #5	$92.56	13.207%	$104.7844	$104.78	$104.80	$104.80
Purchase #6	$166.55	9.511%	$182.3906	$182.39	$182.40	$182.40
Purchase #7	$202.40	11.726%	$226.1334	$226.13	$226.15	$226.10
7 purchase totals =	$978.42		$1,095.9662	$1,095.96	$1,096.00	$1,096.00