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	$99.52	12.422%	$111.8824	$111.88	$111.90	$111.90
Purchase #2	$242.82	9.104%	$264.9263	$264.93	$264.95	$264.90
Purchase #3	$140.27	7.688%	$151.054	$151.05	$151.05	$151.10
Purchase #4	$138.69	11.601%	$154.7794	$154.78	$154.80	$154.80
Purchase #5	$169.79	6.610%	$181.0131	$181.01	$181.00	$181.00
Purchase #6	$107.40	4.705%	$112.4532	$112.45	$112.45	$112.50
Purchase #7	$28.33	10.382%	$31.2712	$31.27	$31.25	$31.30
7 purchase totals =	$926.82		$1,007.3796	$1,007.37	$1,007.40	$1,007.50