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	$187.85	4.771%	$196.8123	$196.81	$196.80	$196.80
Purchase #2	$246.96	13.596%	$280.5367	$280.54	$280.55	$280.50
Purchase #3	$195.40	3.320%	$201.8873	$201.89	$201.90	$201.90
Purchase #4	$118.38	8.176%	$128.0587	$128.06	$128.05	$128.10
Purchase #5	$54.86	7.467%	$58.9564	$58.96	$58.95	$59.00
Purchase #6	$33.85	8.566%	$36.7496	$36.75	$36.75	$36.70
Purchase #7	$173.59	12.407%	$195.1273	$195.13	$195.15	$195.10
7 purchase totals =	$1,010.89		$1,098.1283	$1,098.14	$1,098.15	$1,098.10