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	$59.50	11.216%	$66.1735	$66.17	$66.15	$66.20
Purchase #2	$238.81	13.836%	$271.8518	$271.85	$271.85	$271.90
Purchase #3	$25.76	6.112%	$27.3345	$27.33	$27.35	$27.30
Purchase #4	$159.39	13.256%	$180.5187	$180.52	$180.50	$180.50
Purchase #5	$188.55	13.475%	$213.9571	$213.96	$213.95	$214.00
Purchase #6	$231.69	11.419%	$258.1467	$258.15	$258.15	$258.10
Purchase #7	$101.30	4.275%	$105.6306	$105.63	$105.65	$105.60
7 purchase totals =	$1,005.00		$1,123.6129	$1,123.61	$1,123.60	$1,123.60