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	$209.84	7.588%	$225.7627	$225.76	$225.75	$225.80
Purchase #2	$102.27	12.315%	$114.8646	$114.86	$114.85	$114.90
Purchase #3	$162.59	10.467%	$179.6083	$179.61	$179.60	$179.60
Purchase #4	$97.31	6.783%	$103.9105	$103.91	$103.90	$103.90
Purchase #5	$148.37	8.730%	$161.3227	$161.32	$161.30	$161.30
Purchase #6	$26.74	10.111%	$29.4437	$29.44	$29.45	$29.40
Purchase #7	$50.46	8.153%	$54.574	$54.57	$54.55	$54.60
7 purchase totals =	$797.58		$869.4865	$869.47	$869.40	$869.50