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	$245.69	10.533%	$271.5685	$271.57	$271.55	$271.60
Purchase #2	$39.57	7.349%	$42.478	$42.48	$42.50	$42.50
Purchase #3	$156.82	13.216%	$177.5453	$177.55	$177.55	$177.50
Purchase #4	$216.63	6.739%	$231.2287	$231.23	$231.25	$231.20
Purchase #5	$87.34	8.335%	$94.6198	$94.62	$94.60	$94.60
Purchase #6	$45.61	9.796%	$50.078	$50.08	$50.10	$50.10
Purchase #7	$185.94	12.406%	$209.0077	$209.01	$209.00	$209.00
7 purchase totals =	$977.60		$1,076.5260	$1,076.54	$1,076.55	$1,076.50