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	$209.95	6.427%	$223.4435	$223.44	$223.45	$223.40
Purchase #2	$81.38	10.624%	$90.0258	$90.03	$90.05	$90.00
Purchase #3	$107.77	7.869%	$116.2504	$116.25	$116.25	$116.30
Purchase #4	$188.32	3.871%	$195.6099	$195.61	$195.60	$195.60
Purchase #5	$89.75	13.482%	$101.8501	$101.85	$101.85	$101.90
Purchase #6	$221.45	3.237%	$228.6183	$228.62	$228.60	$228.60
Purchase #7	$112.46	13.724%	$127.894	$127.89	$127.90	$127.90
7 purchase totals =	$1,011.08		$1,083.6920	$1,083.69	$1,083.70	$1,083.70