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	$215.97	3.330%	$223.1618	$223.16	$223.15	$223.20
Purchase #2	$133.50	3.262%	$137.8548	$137.85	$137.85	$137.90
Purchase #3	$222.56	9.856%	$244.4955	$244.50	$244.50	$244.50
Purchase #4	$249.86	8.364%	$270.7583	$270.76	$270.75	$270.80
Purchase #5	$248.81	12.741%	$280.5109	$280.51	$280.50	$280.50
Purchase #6	$223.51	9.844%	$245.5123	$245.51	$245.50	$245.50
Purchase #7	$46.58	4.420%	$48.6388	$48.64	$48.65	$48.60
7 purchase totals =	$1,340.79		$1,450.9324	$1,450.93	$1,450.90	$1,451.00