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	$199.64	9.496%	$218.5978	$218.60	$218.60	$218.60
Purchase #2	$35.59	4.253%	$37.1036	$37.10	$37.10	$37.10
Purchase #3	$42.86	11.746%	$47.8943	$47.89	$47.90	$47.90
Purchase #4	$241.84	6.818%	$258.3287	$258.33	$258.35	$258.30
Purchase #5	$17.81	7.579%	$19.1598	$19.16	$19.15	$19.20
Purchase #6	$61.35	9.535%	$67.1997	$67.20	$67.20	$67.20
Purchase #7	$184.80	6.540%	$196.8859	$196.89	$196.90	$196.90
7 purchase totals =	$783.89		$845.1698	$845.17	$845.20	$845.20