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	$60.91	3.112%	$62.8055	$62.81	$62.80	$62.80
Purchase #2	$192.46	8.724%	$209.2502	$209.25	$209.25	$209.30
Purchase #3	$223.70	4.525%	$233.8224	$233.82	$233.80	$233.80
Purchase #4	$213.98	3.156%	$220.7332	$220.73	$220.75	$220.70
Purchase #5	$68.46	11.361%	$76.2377	$76.24	$76.25	$76.20
Purchase #6	$98.56	4.822%	$103.3126	$103.31	$103.30	$103.30
Purchase #7	$124.82	5.605%	$131.8162	$131.82	$131.80	$131.80
7 purchase totals =	$982.89		$1,037.9778	$1,037.98	$1,037.95	$1,037.90