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	$240.88	4.415%	$251.5149	$251.51	$251.50	$251.50
Purchase #2	$62.65	4.557%	$65.505	$65.51	$65.50	$65.50
Purchase #3	$233.25	8.731%	$253.6151	$253.62	$253.60	$253.60
Purchase #4	$181.86	4.821%	$190.6275	$190.63	$190.65	$190.60
Purchase #5	$11.93	12.141%	$13.3784	$13.38	$13.40	$13.40
Purchase #6	$69.45	12.458%	$78.1021	$78.10	$78.10	$78.10
Purchase #7	$150.34	4.329%	$156.8482	$156.85	$156.85	$156.80
7 purchase totals =	$950.36		$1,009.5912	$1,009.60	$1,009.60	$1,009.50