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	$117.47	9.415%	$128.5298	$128.53	$128.55	$128.50
Purchase #2	$47.39	8.144%	$51.2494	$51.25	$51.25	$51.20
Purchase #3	$156.32	9.724%	$171.5206	$171.52	$171.50	$171.50
Purchase #4	$232.70	5.350%	$245.1495	$245.15	$245.15	$245.10
Purchase #5	$138.65	8.253%	$150.0928	$150.09	$150.10	$150.10
Purchase #6	$235.54	8.321%	$255.1393	$255.14	$255.15	$255.10
Purchase #7	$125.34	13.685%	$142.4928	$142.49	$142.50	$142.50
7 purchase totals =	$1,053.41		$1,144.1742	$1,144.17	$1,144.20	$1,144.00