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	$212.54	6.188%	$225.692	$225.69	$225.70	$225.70
Purchase #2	$104.77	4.280%	$109.2542	$109.25	$109.25	$109.30
Purchase #3	$241.55	12.365%	$271.4177	$271.42	$271.40	$271.40
Purchase #4	$125.60	8.624%	$136.4317	$136.43	$136.45	$136.40
Purchase #5	$245.72	5.208%	$258.5171	$258.52	$258.50	$258.50
Purchase #6	$88.94	9.446%	$97.3413	$97.34	$97.35	$97.30
Purchase #7	$31.85	5.785%	$33.6925	$33.69	$33.70	$33.70
7 purchase totals =	$1,050.97		$1,132.3465	$1,132.34	$1,132.35	$1,132.30