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	$96.64	4.109%	$100.6109	$100.61	$100.60	$100.60
Purchase #2	$121.70	8.524%	$132.0737	$132.07	$132.05	$132.10
Purchase #3	$40.79	7.660%	$43.9145	$43.91	$43.90	$43.90
Purchase #4	$98.81	13.208%	$111.8608	$111.86	$111.85	$111.90
Purchase #5	$206.48	6.364%	$219.6204	$219.62	$219.60	$219.60
Purchase #6	$183.97	6.550%	$196.02	$196.02	$196.00	$196.00
Purchase #7	$192.83	9.559%	$211.2626	$211.26	$211.25	$211.30
7 purchase totals =	$941.22		$1,015.3629	$1,015.35	$1,015.25	$1,015.40