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	$183.59	13.329%	$208.0607	$208.06	$208.05	$208.10
Purchase #2	$219.29	4.667%	$229.5243	$229.52	$229.50	$229.50
Purchase #3	$59.50	6.299%	$63.2479	$63.25	$63.25	$63.20
Purchase #4	$212.96	5.120%	$223.8636	$223.86	$223.85	$223.90
Purchase #5	$90.37	11.605%	$100.8574	$100.86	$100.85	$100.90
Purchase #6	$244.33	9.213%	$266.8401	$266.84	$266.85	$266.80
Purchase #7	$5.46	11.434%	$6.0843	$6.08	$6.10	$6.10
7 purchase totals =	$1,015.50		$1,098.4783	$1,098.47	$1,098.45	$1,098.50