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	$198.59	10.540%	$219.5214	$219.52	$219.50	$219.50
Purchase #2	$112.69	9.610%	$123.5195	$123.52	$123.50	$123.50
Purchase #3	$102.37	9.226%	$111.8147	$111.81	$111.80	$111.80
Purchase #4	$176.36	6.396%	$187.64	$187.64	$187.65	$187.60
Purchase #5	$79.71	7.417%	$85.6221	$85.62	$85.60	$85.60
Purchase #6	$186.61	9.421%	$204.1905	$204.19	$204.20	$204.20
Purchase #7	$200.52	11.236%	$223.0504	$223.05	$223.05	$223.10
7 purchase totals =	$1,056.85		$1,155.3586	$1,155.35	$1,155.30	$1,155.30