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	$150.78	6.214%	$160.1495	$160.15	$160.15	$160.10
Purchase #2	$13.48	12.835%	$15.2102	$15.21	$15.20	$15.20
Purchase #3	$246.50	8.112%	$266.4961	$266.50	$266.50	$266.50
Purchase #4	$97.55	3.639%	$101.0998	$101.10	$101.10	$101.10
Purchase #5	$166.34	8.729%	$180.8598	$180.86	$180.85	$180.90
Purchase #6	$156.34	5.479%	$164.9059	$164.91	$164.90	$164.90
Purchase #7	$101.88	9.792%	$111.8561	$111.86	$111.85	$111.90
7 purchase totals =	$932.87		$1,000.5774	$1,000.59	$1,000.55	$1,000.60