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	$237.92	3.724%	$246.7801	$246.78	$246.80	$246.80
Purchase #2	$241.57	5.870%	$255.7502	$255.75	$255.75	$255.80
Purchase #3	$211.30	13.842%	$240.5481	$240.55	$240.55	$240.50
Purchase #4	$176.63	7.751%	$190.3206	$190.32	$190.30	$190.30
Purchase #5	$218.36	7.236%	$234.1605	$234.16	$234.15	$234.20
Purchase #6	$50.81	3.123%	$52.3968	$52.40	$52.40	$52.40
Purchase #7	$180.58	5.691%	$190.8568	$190.86	$190.85	$190.90
7 purchase totals =	$1,317.17		$1,410.8131	$1,410.82	$1,410.80	$1,410.90