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	$25.43	7.681%	$27.3833	$27.38	$27.40	$27.40
Purchase #2	$72.88	6.125%	$77.3439	$77.34	$77.35	$77.30
Purchase #3	$38.26	6.376%	$40.6995	$40.70	$40.70	$40.70
Purchase #4	$137.69	3.724%	$142.8176	$142.82	$142.80	$142.80
Purchase #5	$139.72	7.715%	$150.4994	$150.50	$150.50	$150.50
Purchase #6	$96.76	12.537%	$108.8908	$108.89	$108.90	$108.90
Purchase #7	$143.68	9.274%	$157.0049	$157.00	$157.00	$157.00
7 purchase totals =	$654.42		$704.6394	$704.63	$704.65	$704.60