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	$102.90	6.713%	$109.8077	$109.81	$109.80	$109.80
Purchase #2	$57.40	7.394%	$61.6442	$61.64	$61.65	$61.60
Purchase #3	$144.42	7.566%	$155.3468	$155.35	$155.35	$155.30
Purchase #4	$178.34	11.449%	$198.7581	$198.76	$198.75	$198.80
Purchase #5	$231.78	11.523%	$258.488	$258.49	$258.50	$258.50
Purchase #6	$99.96	9.653%	$109.6091	$109.61	$109.60	$109.60
Purchase #7	$57.55	11.685%	$64.2747	$64.27	$64.25	$64.30
7 purchase totals =	$872.35		$957.9286	$957.93	$957.90	$957.90