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	$244.71	8.212%	$264.8056	$264.81	$264.80	$264.80
Purchase #2	$30.95	5.591%	$32.6804	$32.68	$32.70	$32.70
Purchase #3	$165.48	12.699%	$186.4943	$186.49	$186.50	$186.50
Purchase #4	$66.99	9.770%	$73.5349	$73.53	$73.55	$73.50
Purchase #5	$63.52	9.443%	$69.5182	$69.52	$69.50	$69.50
Purchase #6	$165.86	12.106%	$185.939	$185.94	$185.95	$185.90
Purchase #7	$170.51	10.622%	$188.6216	$188.62	$188.60	$188.60
7 purchase totals =	$908.02		$1,001.5940	$1,001.59	$1,001.60	$1,001.50