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	$102.80	10.234%	$113.3206	$113.32	$113.30	$113.30
Purchase #2	$71.68	9.252%	$78.3118	$78.31	$78.30	$78.30
Purchase #3	$137.50	13.346%	$155.8508	$155.85	$155.85	$155.90
Purchase #4	$239.27	11.783%	$267.4632	$267.46	$267.45	$267.50
Purchase #5	$123.38	4.167%	$128.5212	$128.52	$128.50	$128.50
Purchase #6	$227.64	8.414%	$246.7936	$246.79	$246.80	$246.80
Purchase #7	$216.27	9.272%	$236.3226	$236.32	$236.30	$236.30
7 purchase totals =	$1,118.54		$1,226.5838	$1,226.57	$1,226.50	$1,226.60