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	$134.35	7.484%	$144.4048	$144.40	$144.40	$144.40
Purchase #2	$198.34	12.239%	$222.6148	$222.61	$222.60	$222.60
Purchase #3	$196.82	4.694%	$206.0587	$206.06	$206.05	$206.10
Purchase #4	$237.83	13.298%	$269.4566	$269.46	$269.45	$269.50
Purchase #5	$170.75	6.398%	$181.6746	$181.67	$181.65	$181.70
Purchase #6	$241.53	9.518%	$264.5188	$264.52	$264.50	$264.50
Purchase #7	$185.97	13.308%	$210.7189	$210.72	$210.70	$210.70
7 purchase totals =	$1,365.59		$1,499.4472	$1,499.44	$1,499.35	$1,499.50