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	$166.43	13.535%	$188.9563	$188.96	$188.95	$189.00
Purchase #2	$184.33	5.746%	$194.9216	$194.92	$194.90	$194.90
Purchase #3	$121.82	8.718%	$132.4403	$132.44	$132.45	$132.40
Purchase #4	$55.27	7.346%	$59.3301	$59.33	$59.35	$59.30
Purchase #5	$148.37	4.348%	$154.8211	$154.82	$154.80	$154.80
Purchase #6	$178.85	4.298%	$186.537	$186.54	$186.55	$186.50
Purchase #7	$134.95	12.864%	$152.31	$152.31	$152.30	$152.30
7 purchase totals =	$990.02		$1,069.3164	$1,069.32	$1,069.30	$1,069.20