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	$216.29	10.535%	$239.0762	$239.08	$239.10	$239.10
Purchase #2	$224.80	6.787%	$240.0572	$240.06	$240.05	$240.10
Purchase #3	$41.71	10.531%	$46.1025	$46.10	$46.10	$46.10
Purchase #4	$73.96	7.177%	$79.2681	$79.27	$79.25	$79.30
Purchase #5	$137.83	6.528%	$146.8275	$146.83	$146.85	$146.80
Purchase #6	$75.36	9.252%	$82.3323	$82.33	$82.35	$82.30
Purchase #7	$160.56	13.733%	$182.6097	$182.61	$182.60	$182.60
7 purchase totals =	$930.51		$1,016.2735	$1,016.28	$1,016.30	$1,016.30