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	$41.83	13.287%	$47.388	$47.39	$47.40	$47.40
Purchase #2	$182.57	7.786%	$196.7849	$196.78	$196.80	$196.80
Purchase #3	$81.69	12.686%	$92.0532	$92.05	$92.05	$92.10
Purchase #4	$181.85	3.770%	$188.7057	$188.71	$188.70	$188.70
Purchase #5	$181.62	13.718%	$206.5346	$206.53	$206.55	$206.50
Purchase #6	$102.98	4.362%	$107.472	$107.47	$107.45	$107.50
Purchase #7	$100.86	10.260%	$111.2082	$111.21	$111.20	$111.20
7 purchase totals =	$873.40		$950.1466	$950.14	$950.15	$950.20