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	$191.72	9.425%	$209.7896	$209.79	$209.80	$209.80
Purchase #2	$95.59	10.348%	$105.4817	$105.48	$105.50	$105.50
Purchase #3	$104.49	13.167%	$118.2482	$118.25	$118.25	$118.20
Purchase #4	$200.36	11.305%	$223.0107	$223.01	$223.00	$223.00
Purchase #5	$36.45	11.644%	$40.6942	$40.69	$40.70	$40.70
Purchase #6	$47.46	12.621%	$53.4499	$53.45	$53.45	$53.40
Purchase #7	$97.96	6.854%	$104.6742	$104.67	$104.65	$104.70
7 purchase totals =	$774.03		$855.3485	$855.34	$855.35	$855.30