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	$136.64	8.252%	$147.9155	$147.92	$147.90	$147.90
Purchase #2	$100.55	6.848%	$107.4357	$107.44	$107.45	$107.40
Purchase #3	$76.75	11.149%	$85.3069	$85.31	$85.30	$85.30
Purchase #4	$39.68	7.388%	$42.6116	$42.61	$42.60	$42.60
Purchase #5	$116.76	12.874%	$131.7917	$131.79	$131.80	$131.80
Purchase #6	$29.68	4.642%	$31.0577	$31.06	$31.05	$31.10
Purchase #7	$161.53	3.638%	$167.4065	$167.41	$167.40	$167.40
7 purchase totals =	$661.59		$713.5256	$713.54	$713.50	$713.50