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	$131.68	8.357%	$142.6845	$142.68	$142.70	$142.70
Purchase #2	$186.44	4.295%	$194.4476	$194.45	$194.45	$194.40
Purchase #3	$81.90	10.320%	$90.3521	$90.35	$90.35	$90.40
Purchase #4	$74.45	7.460%	$80.004	$80.00	$80.00	$80.00
Purchase #5	$179.85	3.444%	$186.044	$186.04	$186.05	$186.00
Purchase #6	$180.71	3.750%	$187.4866	$187.49	$187.50	$187.50
Purchase #7	$141.37	7.850%	$152.4675	$152.47	$152.45	$152.50
7 purchase totals =	$976.40		$1,033.4863	$1,033.48	$1,033.50	$1,033.50