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	$218.39	11.436%	$243.3651	$243.37	$243.35	$243.40
Purchase #2	$71.80	9.217%	$78.4178	$78.42	$78.40	$78.40
Purchase #3	$82.82	3.343%	$85.5887	$85.59	$85.60	$85.60
Purchase #4	$120.39	4.713%	$126.064	$126.06	$126.05	$126.10
Purchase #5	$39.74	10.699%	$43.9918	$43.99	$44.00	$44.00
Purchase #6	$198.29	12.704%	$223.4808	$223.48	$223.50	$223.50
Purchase #7	$205.81	5.784%	$217.7141	$217.71	$217.70	$217.70
7 purchase totals =	$937.24		$1,018.6223	$1,018.62	$1,018.60	$1,018.70