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	$184.90	12.792%	$208.5524	$208.55	$208.55	$208.60
Purchase #2	$61.59	9.545%	$67.4688	$67.47	$67.45	$67.50
Purchase #3	$237.95	11.405%	$265.0882	$265.09	$265.10	$265.10
Purchase #4	$237.50	4.416%	$247.988	$247.99	$248.00	$248.00
Purchase #5	$90.40	4.623%	$94.5792	$94.58	$94.60	$94.60
Purchase #6	$140.94	8.299%	$152.6366	$152.64	$152.65	$152.60
Purchase #7	$156.57	3.557%	$162.1392	$162.14	$162.15	$162.10
7 purchase totals =	$1,109.85		$1,198.4524	$1,198.46	$1,198.50	$1,198.50