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	$239.98	9.542%	$262.8789	$262.88	$262.90	$262.90
Purchase #2	$232.79	3.342%	$240.5698	$240.57	$240.55	$240.60
Purchase #3	$156.25	5.250%	$164.4531	$164.45	$164.45	$164.50
Purchase #4	$51.83	6.669%	$55.2865	$55.29	$55.30	$55.30
Purchase #5	$171.86	5.772%	$181.7798	$181.78	$181.80	$181.80
Purchase #6	$243.54	11.480%	$271.4984	$271.50	$271.50	$271.50
Purchase #7	$70.71	9.360%	$77.3285	$77.33	$77.35	$77.30
7 purchase totals =	$1,166.96		$1,253.7950	$1,253.80	$1,253.85	$1,253.90