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	$182.48	11.466%	$203.4032	$203.40	$203.40	$203.40
Purchase #2	$215.76	5.596%	$227.8339	$227.83	$227.85	$227.80
Purchase #3	$226.94	12.315%	$254.8877	$254.89	$254.90	$254.90
Purchase #4	$163.51	9.830%	$179.583	$179.58	$179.60	$179.60
Purchase #5	$38.60	10.398%	$42.6136	$42.61	$42.60	$42.60
Purchase #6	$51.40	3.419%	$53.1574	$53.16	$53.15	$53.20
Purchase #7	$69.93	12.317%	$78.5433	$78.54	$78.55	$78.50
7 purchase totals =	$948.62		$1,040.0221	$1,040.01	$1,040.05	$1,040.00